diff --git a/eval.c b/eval.c
index e93f8edc..f2575de9 100644
--- a/eval.c
+++ b/eval.c
@@ -291,7 +291,7 @@ sexp sexp_make_context(sexp ctx, sexp stack, sexp env) {
   }
   sexp_context_stack(res) = stack;
   sexp_context_env(res)
-    = (env ? env : sexp_make_standard_env(res, sexp_make_integer(5)));
+    = (env ? env : sexp_make_standard_env(res, sexp_make_fixnum(5)));
   sexp_context_bc(res)
     = sexp_alloc_tagged(ctx, sexp_sizeof(bytecode)+INIT_BCODE_SIZE,
                         SEXP_BYTECODE);
@@ -690,9 +690,9 @@ static sexp analyze (sexp ctx, sexp object) {
 /*           res = analyze(tmp, x); */
         } else if (sexp_opcodep(op)) {
           res = sexp_length(ctx, sexp_cdr(x));
-          if (sexp_unbox_integer(res) < sexp_opcode_num_args(op)) {
+          if (sexp_unbox_fixnum(res) < sexp_opcode_num_args(op)) {
             res = sexp_compile_error(ctx, "not enough args for opcode", x);
-          } else if ((sexp_unbox_integer(res) > sexp_opcode_num_args(op))
+          } else if ((sexp_unbox_fixnum(res) > sexp_opcode_num_args(op))
                      && (! sexp_opcode_variadic_p(op))) {
             res = sexp_compile_error(ctx, "too many args for opcode", x);
           } else {
@@ -855,7 +855,7 @@ static void generate_opcode_app (sexp ctx, sexp app) {
   sexp_gc_var1(ls);
   sexp_gc_preserve1(ctx, ls);
 
-  num_args = sexp_unbox_integer(sexp_length(ctx, sexp_cdr(app)));
+  num_args = sexp_unbox_fixnum(sexp_length(ctx, sexp_cdr(app)));
   sexp_context_tailp(ctx) = 0;
 
   /* maybe push the default for an optional argument */
@@ -935,7 +935,7 @@ static void generate_opcode_app (sexp ctx, sexp app) {
 }
 
 static void generate_general_app (sexp ctx, sexp app) {
-  sexp_uint_t len = sexp_unbox_integer(sexp_length(ctx, sexp_cdr(app))),
+  sexp_uint_t len = sexp_unbox_fixnum(sexp_length(ctx, sexp_cdr(app))),
     tailp = sexp_context_tailp(ctx);
   sexp_gc_var1(ls);
   sexp_gc_preserve1(ctx, ls);
@@ -950,7 +950,7 @@ static void generate_general_app (sexp ctx, sexp app) {
 
   /* maybe overwrite the current frame */
   emit(ctx, (tailp ? OP_TAIL_CALL : OP_CALL));
-  emit_word(ctx, (sexp_uint_t)sexp_make_integer(len));
+  emit_word(ctx, (sexp_uint_t)sexp_make_fixnum(len));
 
   sexp_context_depth(ctx) -= len;
   sexp_gc_release1(ctx);
@@ -991,14 +991,14 @@ static void generate_lambda (sexp ctx, sexp lambda) {
   }
   sexp_context_tailp(ctx2) = 1;
   generate(ctx2, sexp_lambda_body(lambda));
-  flags = sexp_make_integer((sexp_listp(ctx2, sexp_lambda_params(lambda))
+  flags = sexp_make_fixnum((sexp_listp(ctx2, sexp_lambda_params(lambda))
                              == SEXP_FALSE) ? 1uL : 0uL);
   len = sexp_length(ctx2, sexp_lambda_params(lambda));
   bc = finalize_bytecode(ctx2);
   sexp_bytecode_name(bc) = sexp_lambda_name(lambda);
   if (sexp_nullp(fv)) {
     /* shortcut, no free vars */
-    tmp = sexp_make_vector(ctx2, sexp_make_integer(0), SEXP_VOID);
+    tmp = sexp_make_vector(ctx2, sexp_make_fixnum(0), SEXP_VOID);
     tmp = sexp_make_procedure(ctx2, flags, len, bc, tmp);
     sexp_push(ctx, sexp_bytecode_literals(sexp_context_bc(ctx)), tmp);
     generate_lit(ctx, tmp);
@@ -1012,7 +1012,7 @@ static void generate_lambda (sexp ctx, sexp lambda) {
       ref = sexp_car(fv);
       generate_non_global_ref(ctx, sexp_ref_name(ref), sexp_ref_cell(ref),
                               prev_lambda, prev_fv, 0);
-      emit_push(ctx, sexp_make_integer(k));
+      emit_push(ctx, sexp_make_fixnum(k));
       emit(ctx, OP_STACK_REF);
       emit_word(ctx, 3);
       emit(ctx, OP_VECTOR_SET);
@@ -1116,7 +1116,7 @@ static sexp make_param_list(sexp ctx, sexp_uint_t i) {
   sexp_gc_preserve1(ctx, res);
   res = SEXP_NULL;
   for ( ; i>0; i--)
-    res = sexp_cons(ctx, sexp_make_integer(i), res);
+    res = sexp_cons(ctx, sexp_make_fixnum(i), res);
   sexp_gc_release1(ctx);
   return res;
 }
@@ -1141,7 +1141,7 @@ static sexp make_opcode_procedure (sexp ctx, sexp op, sexp_uint_t i) {
   generate_opcode_app(ctx2, refs);
   bc = finalize_bytecode(ctx2);
   sexp_bytecode_name(bc) = sexp_c_string(ctx2, sexp_opcode_name(op), -1);
-  res = sexp_make_procedure(ctx2, sexp_make_integer(0), sexp_make_integer(i),
+  res = sexp_make_procedure(ctx2, sexp_make_fixnum(0), sexp_make_fixnum(i),
                             bc, SEXP_VOID);
   if (i == sexp_opcode_num_args(op))
     sexp_opcode_proc(op) = res;
@@ -1154,7 +1154,7 @@ static sexp make_opcode_procedure (sexp ctx, sexp op, sexp_uint_t i) {
 static sexp sexp_save_stack(sexp ctx, sexp *stack, sexp_uint_t to) {
   sexp res, *data;
   sexp_uint_t i;
-  res = sexp_make_vector(ctx, sexp_make_integer(to), SEXP_VOID);
+  res = sexp_make_vector(ctx, sexp_make_fixnum(to), SEXP_VOID);
   data = sexp_vector_data(res);
   for (i=0; i<to; i++)
     data[i] = stack[i];
@@ -1221,9 +1221,9 @@ sexp sexp_vm (sexp ctx, sexp proc) {
   case OP_RAISE:
   call_error_handler:
     stack[top] = (sexp) 1;
-    stack[top+1] = sexp_make_integer(ip-sexp_bytecode_data(bc));
+    stack[top+1] = sexp_make_fixnum(ip-sexp_bytecode_data(bc));
     stack[top+2] = self;
-    stack[top+3] = sexp_make_integer(fp);
+    stack[top+3] = sexp_make_fixnum(fp);
     top += 4;
     self = env_global_ref(env, the_err_handler_symbol, SEXP_FALSE);
     bc = sexp_procedure_code(self);
@@ -1234,29 +1234,29 @@ sexp sexp_vm (sexp ctx, sexp proc) {
   case OP_RESUMECC:
     tmp1 = stack[fp-1];
     top = sexp_restore_stack(sexp_vector_ref(cp, 0), stack);
-    fp = sexp_unbox_integer(_ARG1);
+    fp = sexp_unbox_fixnum(_ARG1);
     self = _ARG2;
     bc = sexp_procedure_code(self);
     cp = sexp_procedure_vars(self);
-    ip = sexp_bytecode_data(bc) + sexp_unbox_integer(_ARG3);
-    i = sexp_unbox_integer(_ARG4);
+    ip = sexp_bytecode_data(bc) + sexp_unbox_fixnum(_ARG3);
+    i = sexp_unbox_fixnum(_ARG4);
     top -= 4;
     _ARG1 = tmp1;
     break;
   case OP_CALLCC:
-    stack[top] = sexp_make_integer(1);
-    stack[top+1] = sexp_make_integer(ip-sexp_bytecode_data(bc));
+    stack[top] = sexp_make_fixnum(1);
+    stack[top+1] = sexp_make_fixnum(ip-sexp_bytecode_data(bc));
     stack[top+2] = self;
-    stack[top+3] = sexp_make_integer(fp);
+    stack[top+3] = sexp_make_fixnum(fp);
     tmp1 = _ARG1;
     i = 1;
     sexp_context_top(ctx) = top;
-    tmp2 = sexp_make_vector(ctx, sexp_make_integer(1), SEXP_UNDEF);
+    tmp2 = sexp_make_vector(ctx, sexp_make_fixnum(1), SEXP_UNDEF);
     sexp_vector_set(tmp2,
-                    sexp_make_integer(0),
+                    sexp_make_fixnum(0),
                     sexp_save_stack(ctx, stack, top+4));
-    _ARG1 = sexp_make_procedure(ctx, sexp_make_integer(0),
-                                sexp_make_integer(1), continuation_resumer,
+    _ARG1 = sexp_make_procedure(ctx, sexp_make_fixnum(0),
+                                sexp_make_fixnum(1), continuation_resumer,
                                 tmp2);
     top++;
     ip -= sizeof(sexp);
@@ -1264,7 +1264,7 @@ sexp sexp_vm (sexp ctx, sexp proc) {
   case OP_APPLY1:
     tmp1 = _ARG1;
     tmp2 = _ARG2;
-    i = sexp_unbox_integer(sexp_length(ctx, tmp2));
+    i = sexp_unbox_fixnum(sexp_length(ctx, tmp2));
     top += (i-2);
     for ( ; sexp_pairp(tmp2); tmp2=sexp_cdr(tmp2), top--)
       _ARG1 = sexp_car(tmp2);
@@ -1272,28 +1272,28 @@ sexp sexp_vm (sexp ctx, sexp proc) {
     ip -= sizeof(sexp);
     goto make_call;
   case OP_TAIL_CALL:
-    i = sexp_unbox_integer(_WORD0);    /* number of params */
+    i = sexp_unbox_fixnum(_WORD0);    /* number of params */
     tmp1 = _ARG1;                              /* procedure to call */
     /* save frame info */
     tmp2 = stack[fp+3];
-    j = sexp_unbox_integer(stack[fp]);
+    j = sexp_unbox_fixnum(stack[fp]);
     self = stack[fp+2];
     bc = sexp_procedure_vars(self);
     cp = sexp_procedure_vars(self);
     ip = (sexp_bytecode_data(bc)
-          + sexp_unbox_integer(stack[fp+1])) - sizeof(sexp);
+          + sexp_unbox_fixnum(stack[fp+1])) - sizeof(sexp);
     /* copy new args into place */
     for (k=0; k<i; k++)
       stack[fp-j+k] = stack[top-1-i+k];
     top = fp+i-j+1;
-    fp = sexp_unbox_integer(tmp2);
+    fp = sexp_unbox_fixnum(tmp2);
     goto make_call;
   case OP_CALL:
 #if USE_CHECK_STACK
     if (top+16 >= INIT_STACK_SIZE)
       errx(70, "out of stack space at %ld", top);
 #endif
-    i = sexp_unbox_integer(_WORD0);
+    i = sexp_unbox_fixnum(_WORD0);
     tmp1 = _ARG1;
   make_call:
     if (sexp_opcodep(tmp1)) {
@@ -1307,10 +1307,10 @@ sexp sexp_vm (sexp ctx, sexp proc) {
     }
     if (! sexp_procedurep(tmp1))
       sexp_raise("non procedure application", sexp_list1(ctx, tmp1));
-    j = i - sexp_unbox_integer(sexp_procedure_num_args(tmp1));
+    j = i - sexp_unbox_fixnum(sexp_procedure_num_args(tmp1));
     if (j < 0)
       sexp_raise("not enough args",
-                 sexp_list2(ctx, tmp1, sexp_make_integer(i)));
+                 sexp_list2(ctx, tmp1, sexp_make_fixnum(i)));
     if (j > 0) {
       if (sexp_procedure_variadic_p(tmp1)) {
         stack[top-i-1] = sexp_cons(ctx, stack[top-i-1], SEXP_NULL);
@@ -1322,7 +1322,7 @@ sexp sexp_vm (sexp ctx, sexp proc) {
         i -= (j-1);
       } else {
         sexp_raise("too many args",
-                   sexp_list2(ctx, tmp1, sexp_make_integer(i)));
+                   sexp_list2(ctx, tmp1, sexp_make_fixnum(i)));
       }
     } else if (sexp_procedure_variadic_p(tmp1)) {
       /* shift stack, set extra arg to null */
@@ -1332,10 +1332,10 @@ sexp sexp_vm (sexp ctx, sexp proc) {
       top++;
       i++;
     }
-    _ARG1 = sexp_make_integer(i);
-    stack[top] = sexp_make_integer(ip+sizeof(sexp)-sexp_bytecode_data(bc));
+    _ARG1 = sexp_make_fixnum(i);
+    stack[top] = sexp_make_fixnum(ip+sizeof(sexp)-sexp_bytecode_data(bc));
     stack[top+1] = self;
-    stack[top+2] = sexp_make_integer(fp);
+    stack[top+2] = sexp_make_fixnum(fp);
     top += 3;
     self = tmp1;
     bc = sexp_procedure_code(self);
@@ -1436,7 +1436,7 @@ sexp sexp_vm (sexp ctx, sexp proc) {
     ip += sizeof(sexp);
     break;
   case OP_CLOSURE_REF:
-    _PUSH(sexp_vector_ref(cp, sexp_make_integer(_WORD0)));
+    _PUSH(sexp_vector_ref(cp, sexp_make_fixnum(_WORD0)));
     ip += sizeof(sexp);
     break;
   case OP_VECTOR_REF:
@@ -1455,7 +1455,7 @@ sexp sexp_vm (sexp ctx, sexp proc) {
     top-=2;
     break;
   case OP_VECTOR_LENGTH:
-    _ARG1 = sexp_make_integer(sexp_vector_length(_ARG1));
+    _ARG1 = sexp_make_fixnum(sexp_vector_length(_ARG1));
     break;
   case OP_STRING_REF:
     _ARG2 = sexp_string_ref(_ARG1, _ARG2);
@@ -1471,7 +1471,7 @@ sexp sexp_vm (sexp ctx, sexp proc) {
     top-=2;
     break;
   case OP_STRING_LENGTH:
-    _ARG1 = sexp_make_integer(sexp_string_length(_ARG1));
+    _ARG1 = sexp_make_fixnum(sexp_string_length(_ARG1));
     break;
   case OP_MAKE_PROCEDURE:
     sexp_context_top(ctx) = top;
@@ -1493,9 +1493,6 @@ sexp sexp_vm (sexp ctx, sexp proc) {
     _ARG1 = sexp_make_boolean(sexp_nullp(_ARG1)); break;
   case OP_INTEGERP:
     j = sexp_integerp(_ARG1);
-#if USE_BIGNUMS
-    if (! j) j = sexp_bignump(_ARG1);
-#endif
 #if USE_FLONUMS
     if (! j)
       j = (sexp_flonump(_ARG1)
@@ -1509,7 +1506,7 @@ sexp sexp_vm (sexp ctx, sexp proc) {
     _ARG1 = sexp_make_boolean(sexp_charp(_ARG1)); break;
   case OP_TYPEP:
     _ARG1 = sexp_make_boolean(sexp_pointerp(_ARG1)
-                              && (sexp_make_integer(sexp_pointer_tag(_ARG1))
+                              && (sexp_make_fixnum(sexp_pointer_tag(_ARG1))
                                   == _WORD0));
     ip += sizeof(sexp);
     break;
@@ -1547,25 +1544,25 @@ sexp sexp_vm (sexp ctx, sexp proc) {
   case OP_ADD:
 #if USE_BIGNUMS
     tmp1 = _ARG1, tmp2 = _ARG2;
-    if (sexp_integerp(tmp1) && sexp_integerp(tmp2)) {
-      j = sexp_unbox_integer(tmp1) + sexp_unbox_integer(tmp2);
+    if (sexp_fixnump(tmp1) && sexp_fixnump(tmp2)) {
+      j = sexp_unbox_fixnum(tmp1) + sexp_unbox_fixnum(tmp2);
       if ((j < SEXP_MIN_FIXNUM) || (j > SEXP_MAX_FIXNUM))
         _ARG2 = sexp_add(ctx, tmp1=sexp_fixnum_to_bignum(ctx, tmp1), tmp2);
       else
-        _ARG2 = sexp_make_integer(j);
+        _ARG2 = sexp_make_fixnum(j);
     }
     else
       _ARG2 = sexp_add(ctx, tmp1, tmp2);
 #else
-    if (sexp_integerp(_ARG1) && sexp_integerp(_ARG2))
+    if (sexp_fixnump(_ARG1) && sexp_fixnump(_ARG2))
       _ARG2 = sexp_fx_add(_ARG1, _ARG2);
 #if USE_FLONUMS
     else if (sexp_flonump(_ARG1) && sexp_flonump(_ARG2))
       _ARG2 = sexp_fp_add(ctx, _ARG1, _ARG2);
-    else if (sexp_flonump(_ARG1) && sexp_integerp(_ARG2))
-      _ARG2 = sexp_make_flonum(ctx, sexp_flonum_value(_ARG1) + (double)sexp_unbox_integer(_ARG2));
-    else if (sexp_integerp(_ARG1) && sexp_flonump(_ARG2))
-      _ARG2 = sexp_make_flonum(ctx, (double)sexp_unbox_integer(_ARG1) + sexp_flonum_value(_ARG2));
+    else if (sexp_flonump(_ARG1) && sexp_fixnump(_ARG2))
+      _ARG2 = sexp_make_flonum(ctx, sexp_flonum_value(_ARG1) + (double)sexp_unbox_fixnum(_ARG2));
+    else if (sexp_fixnump(_ARG1) && sexp_flonump(_ARG2))
+      _ARG2 = sexp_make_flonum(ctx, (double)sexp_unbox_fixnum(_ARG1) + sexp_flonum_value(_ARG2));
 #endif
     else sexp_raise("+: not a number", sexp_list2(ctx, _ARG1, _ARG2));
 #endif
@@ -1574,25 +1571,25 @@ sexp sexp_vm (sexp ctx, sexp proc) {
   case OP_SUB:
 #if USE_BIGNUMS
     tmp1 = _ARG1, tmp2 = _ARG2;
-    if (sexp_integerp(tmp1) && sexp_integerp(tmp2)) {
-      j = sexp_unbox_integer(tmp1) - sexp_unbox_integer(tmp2);
+    if (sexp_fixnump(tmp1) && sexp_fixnump(tmp2)) {
+      j = sexp_unbox_fixnum(tmp1) - sexp_unbox_fixnum(tmp2);
       if ((j < SEXP_MIN_FIXNUM) || (j > SEXP_MAX_FIXNUM))
         _ARG2 = sexp_sub(ctx, tmp1=sexp_fixnum_to_bignum(ctx, tmp1), tmp2);
       else
-        _ARG2 = sexp_make_integer(j);
+        _ARG2 = sexp_make_fixnum(j);
     }
     else
       _ARG2 = sexp_sub(ctx, tmp1, tmp2);
 #else
-    if (sexp_integerp(_ARG1) && sexp_integerp(_ARG2))
+    if (sexp_fixnump(_ARG1) && sexp_fixnump(_ARG2))
       _ARG2 = sexp_fx_sub(_ARG1, _ARG2);
 #if USE_FLONUMS
     else if (sexp_flonump(_ARG1) && sexp_flonump(_ARG2))
       _ARG2 = sexp_fp_sub(ctx, _ARG1, _ARG2);
-    else if (sexp_flonump(_ARG1) && sexp_integerp(_ARG2))
-      _ARG2 = sexp_make_flonum(ctx, sexp_flonum_value(_ARG1) - (double)sexp_unbox_integer(_ARG2));
-    else if (sexp_integerp(_ARG1) && sexp_flonump(_ARG2))
-      _ARG2 = sexp_make_flonum(ctx, (double)sexp_unbox_integer(_ARG1) - sexp_flonum_value(_ARG2));
+    else if (sexp_flonump(_ARG1) && sexp_fixnump(_ARG2))
+      _ARG2 = sexp_make_flonum(ctx, sexp_flonum_value(_ARG1) - (double)sexp_unbox_fixnum(_ARG2));
+    else if (sexp_fixnump(_ARG1) && sexp_flonump(_ARG2))
+      _ARG2 = sexp_make_flonum(ctx, (double)sexp_unbox_fixnum(_ARG1) - sexp_flonum_value(_ARG2));
 #endif
     else sexp_raise("-: not a number", sexp_list2(ctx, _ARG1, _ARG2));
 #endif
@@ -1601,45 +1598,45 @@ sexp sexp_vm (sexp ctx, sexp proc) {
   case OP_MUL:
 #if USE_BIGNUMS
     tmp1 = _ARG1, tmp2 = _ARG2;
-    if (sexp_integerp(tmp1) && sexp_integerp(tmp2)) {
-      prod = sexp_unbox_integer(tmp1) * sexp_unbox_integer(tmp2);
+    if (sexp_fixnump(tmp1) && sexp_fixnump(tmp2)) {
+      prod = sexp_unbox_fixnum(tmp1) * sexp_unbox_fixnum(tmp2);
       if ((prod < SEXP_MIN_FIXNUM) || (prod > SEXP_MAX_FIXNUM))
         _ARG2 = sexp_mul(ctx, tmp1=sexp_fixnum_to_bignum(ctx, tmp1), tmp2);
       else
-        _ARG2 = sexp_make_integer(prod);
+        _ARG2 = sexp_make_fixnum(prod);
     }
     else
       _ARG2 = sexp_mul(ctx, tmp1, tmp2);
 #else
-    if (sexp_integerp(_ARG1) && sexp_integerp(_ARG2))
+    if (sexp_fixnump(_ARG1) && sexp_fixnump(_ARG2))
       _ARG2 = sexp_fx_mul(_ARG1, _ARG2);
 #if USE_FLONUMS
     else if (sexp_flonump(_ARG1) && sexp_flonump(_ARG2))
       _ARG2 = sexp_fp_mul(ctx, _ARG1, _ARG2);
-    else if (sexp_flonump(_ARG1) && sexp_integerp(_ARG2))
-      _ARG2 = sexp_make_flonum(ctx, sexp_flonum_value(_ARG1) * (double)sexp_unbox_integer(_ARG2));
-    else if (sexp_integerp(_ARG1) && sexp_flonump(_ARG2))
-      _ARG2 = sexp_make_flonum(ctx, (double)sexp_unbox_integer(_ARG1) * sexp_flonum_value(_ARG2));
+    else if (sexp_flonump(_ARG1) && sexp_fixnump(_ARG2))
+      _ARG2 = sexp_make_flonum(ctx, sexp_flonum_value(_ARG1) * (double)sexp_unbox_fixnum(_ARG2));
+    else if (sexp_fixnump(_ARG1) && sexp_flonump(_ARG2))
+      _ARG2 = sexp_make_flonum(ctx, (double)sexp_unbox_fixnum(_ARG1) * sexp_flonum_value(_ARG2));
 #endif
     else sexp_raise("*: not a number", sexp_list2(ctx, _ARG1, _ARG2));
 #endif
     top--;
     break;
   case OP_DIV:
-    if (_ARG2 == sexp_make_integer(0)) {
+    if (_ARG2 == sexp_make_fixnum(0)) {
 #if USE_FLONUMS
       if (sexp_flonump(_ARG1) && sexp_flonum_value(_ARG1) == 0.0)
         _ARG2 = sexp_make_flonum(ctx, 0.0/0.0);
       else
 #endif
         sexp_raise("divide by zero", SEXP_NULL);
-    } else if (sexp_integerp(_ARG1) && sexp_integerp(_ARG2)) {
+    } else if (sexp_fixnump(_ARG1) && sexp_fixnump(_ARG2)) {
 #if USE_FLONUMS
-      _ARG1 = sexp_integer_to_flonum(ctx, _ARG1);
-      _ARG2 = sexp_integer_to_flonum(ctx, _ARG2);
+      _ARG1 = sexp_fixnum_to_flonum(ctx, _ARG1);
+      _ARG2 = sexp_fixnum_to_flonum(ctx, _ARG2);
       _ARG2 = sexp_fp_div(ctx, _ARG1, _ARG2);
       if (sexp_flonum_value(_ARG2) == trunc(sexp_flonum_value(_ARG2)))
-        _ARG2 = sexp_make_integer(sexp_flonum_value(_ARG2));
+        _ARG2 = sexp_make_fixnum(sexp_flonum_value(_ARG2));
 #else
       _ARG2 = sexp_fx_div(_ARG1, _ARG2);
 #endif
@@ -1651,18 +1648,18 @@ sexp sexp_vm (sexp ctx, sexp proc) {
 #if USE_FLONUMS
     else if (sexp_flonump(_ARG1) && sexp_flonump(_ARG2))
       _ARG2 = sexp_fp_div(ctx, _ARG1, _ARG2);
-    else if (sexp_flonump(_ARG1) && sexp_integerp(_ARG2))
-      _ARG2 = sexp_make_flonum(ctx, sexp_flonum_value(_ARG1) / (double)sexp_unbox_integer(_ARG2));
-    else if (sexp_integerp(_ARG1) && sexp_flonump(_ARG2))
-      _ARG2 = sexp_make_flonum(ctx, (double)sexp_unbox_integer(_ARG1) / sexp_flonum_value(_ARG2));
+    else if (sexp_flonump(_ARG1) && sexp_fixnump(_ARG2))
+      _ARG2 = sexp_make_flonum(ctx, sexp_flonum_value(_ARG1) / (double)sexp_unbox_fixnum(_ARG2));
+    else if (sexp_fixnump(_ARG1) && sexp_flonump(_ARG2))
+      _ARG2 = sexp_make_flonum(ctx, (double)sexp_unbox_fixnum(_ARG1) / sexp_flonum_value(_ARG2));
 #endif
     else sexp_raise("/: not a number", sexp_list2(ctx, _ARG1, _ARG2));
 #endif
     top--;
     break;
   case OP_QUOTIENT:
-    if (sexp_integerp(_ARG1) && sexp_integerp(_ARG2)) {
-      if (_ARG2 == sexp_make_integer(0))
+    if (sexp_fixnump(_ARG1) && sexp_fixnump(_ARG2)) {
+      if (_ARG2 == sexp_make_fixnum(0))
         sexp_raise("divide by zero", SEXP_NULL);
       _ARG2 = sexp_fx_div(_ARG1, _ARG2);
       top--;
@@ -1677,8 +1674,8 @@ sexp sexp_vm (sexp ctx, sexp proc) {
 #endif
     break;
   case OP_REMAINDER:
-    if (sexp_integerp(_ARG1) && sexp_integerp(_ARG2)) {
-      if (_ARG2 == sexp_make_integer(0))
+    if (sexp_fixnump(_ARG1) && sexp_fixnump(_ARG2)) {
+      if (_ARG2 == sexp_make_fixnum(0))
         sexp_raise("divide by zero", SEXP_NULL);
       tmp1 = sexp_fx_rem(_ARG1, _ARG2);
       top--;
@@ -1694,8 +1691,8 @@ sexp sexp_vm (sexp ctx, sexp proc) {
 #endif
     break;
   case OP_NEGATIVE:
-    if (sexp_integerp(_ARG1))
-      _ARG1 = sexp_make_integer(-sexp_unbox_integer(_ARG1));
+    if (sexp_fixnump(_ARG1))
+      _ARG1 = sexp_make_fixnum(-sexp_unbox_fixnum(_ARG1));
 #if USE_BIGNUMS
     else if (sexp_bignump(_ARG1)) {
       _ARG1 = sexp_copy_bignum(ctx, NULL, _ARG1, 0);
@@ -1709,8 +1706,8 @@ sexp sexp_vm (sexp ctx, sexp proc) {
     else sexp_raise("-: not a number", sexp_list1(ctx, _ARG1));
     break;
   case OP_INVERSE:
-    if (sexp_integerp(_ARG1))
-      _ARG1 = sexp_make_flonum(ctx, 1/(double)sexp_unbox_integer(_ARG1));
+    if (sexp_fixnump(_ARG1))
+      _ARG1 = sexp_make_flonum(ctx, 1/(double)sexp_unbox_fixnum(_ARG1));
 #if USE_FLONUMS
     else if (sexp_flonump(_ARG1))
       _ARG1 = sexp_make_flonum(ctx, 1/sexp_flonum_value(_ARG1));
@@ -1718,23 +1715,23 @@ sexp sexp_vm (sexp ctx, sexp proc) {
     else sexp_raise("/: not a number", sexp_list1(ctx, _ARG1));
     break;
   case OP_LT:
-    if (sexp_integerp(_ARG1) && sexp_integerp(_ARG2)) {
+    if (sexp_fixnump(_ARG1) && sexp_fixnump(_ARG2)) {
       i = (sexp_sint_t)_ARG1 < (sexp_sint_t)_ARG2;
 #if USE_BIGNUMS
       _ARG2 = sexp_make_boolean(i);
     } else {
       tmp1 = sexp_compare(ctx, _ARG1, _ARG2);
-      _ARG2 = sexp_integerp(tmp1)
-        ? sexp_make_boolean(sexp_unbox_integer(tmp1) < 0) : tmp1;
+      _ARG2 = sexp_fixnump(tmp1)
+        ? sexp_make_boolean(sexp_unbox_fixnum(tmp1) < 0) : tmp1;
     }
 #else
 #if USE_FLONUMS
     } else if (sexp_flonump(_ARG1) && sexp_flonump(_ARG2))
       i = sexp_flonum_value(_ARG1) < sexp_flonum_value(_ARG2);
-    else if (sexp_flonump(_ARG1) && sexp_integerp(_ARG2))
-      i = sexp_flonum_value(_ARG1) < (double)sexp_unbox_integer(_ARG2);
-    else if (sexp_integerp(_ARG1) && sexp_flonump(_ARG2))
-      i = (double)sexp_unbox_integer(_ARG1) < sexp_flonum_value(_ARG2);
+    else if (sexp_flonump(_ARG1) && sexp_fixnump(_ARG2))
+      i = sexp_flonum_value(_ARG1) < (double)sexp_unbox_fixnum(_ARG2);
+    else if (sexp_fixnump(_ARG1) && sexp_flonump(_ARG2))
+      i = (double)sexp_unbox_fixnum(_ARG1) < sexp_flonum_value(_ARG2);
 #endif
     else sexp_raise("<: not a number", sexp_list2(ctx, _ARG1, _ARG2));
     _ARG2 = sexp_make_boolean(i);
@@ -1742,23 +1739,23 @@ sexp sexp_vm (sexp ctx, sexp proc) {
     top--;
     break;
   case OP_LE:
-    if (sexp_integerp(_ARG1) && sexp_integerp(_ARG2)) {
+    if (sexp_fixnump(_ARG1) && sexp_fixnump(_ARG2)) {
       i = (sexp_sint_t)_ARG1 <= (sexp_sint_t)_ARG2;
 #if USE_BIGNUMS
       _ARG2 = sexp_make_boolean(i);
     } else {
       tmp1 = sexp_compare(ctx, _ARG1, _ARG2);
-      _ARG2 = sexp_integerp(tmp1)
-        ? sexp_make_boolean(sexp_unbox_integer(tmp1) <= 0) : tmp1;
+      _ARG2 = sexp_fixnump(tmp1)
+        ? sexp_make_boolean(sexp_unbox_fixnum(tmp1) <= 0) : tmp1;
     }
 #else
 #if USE_FLONUMS
     } else if (sexp_flonump(_ARG1) && sexp_flonump(_ARG2))
       i = sexp_flonum_value(_ARG1) <= sexp_flonum_value(_ARG2);
-    else if (sexp_flonump(_ARG1) && sexp_integerp(_ARG2))
-      i = sexp_flonum_value(_ARG1) <= (double)sexp_unbox_integer(_ARG2);
-    else if (sexp_integerp(_ARG1) && sexp_flonump(_ARG2))
-      i = (double)sexp_unbox_integer(_ARG1) <= sexp_flonum_value(_ARG2);
+    else if (sexp_flonump(_ARG1) && sexp_fixnump(_ARG2))
+      i = sexp_flonum_value(_ARG1) <= (double)sexp_unbox_fixnum(_ARG2);
+    else if (sexp_fixnump(_ARG1) && sexp_flonump(_ARG2))
+      i = (double)sexp_unbox_fixnum(_ARG1) <= sexp_flonum_value(_ARG2);
 #endif
     else sexp_raise("<=: not a number", sexp_list2(ctx, _ARG1, _ARG2));
     _ARG2 = sexp_make_boolean(i);
@@ -1766,23 +1763,23 @@ sexp sexp_vm (sexp ctx, sexp proc) {
     top--;
     break;
   case OP_EQN:
-    if (sexp_integerp(_ARG1) && sexp_integerp(_ARG2)) {
+    if (sexp_fixnump(_ARG1) && sexp_fixnump(_ARG2)) {
       i = _ARG1 == _ARG2;
 #if USE_BIGNUMS
       _ARG2 = sexp_make_boolean(i);
     } else {
       tmp1 = sexp_compare(ctx, _ARG1, _ARG2);
-      _ARG2 = sexp_integerp(tmp1)
-        ? sexp_make_boolean(sexp_unbox_integer(tmp1) == 0) : tmp1;
+      _ARG2 = sexp_fixnump(tmp1)
+        ? sexp_make_boolean(sexp_unbox_fixnum(tmp1) == 0) : tmp1;
     }
 #else
 #if USE_FLONUMS
     } else if (sexp_flonump(_ARG1) && sexp_flonump(_ARG2))
       i = sexp_flonum_value(_ARG1) == sexp_flonum_value(_ARG2);
-    else if (sexp_flonump(_ARG1) && sexp_integerp(_ARG2))
-      i = sexp_flonum_value(_ARG1) == (double)sexp_unbox_integer(_ARG2);
-    else if (sexp_integerp(_ARG1) && sexp_flonump(_ARG2))
-      i = (double)sexp_unbox_integer(_ARG1) == sexp_flonum_value(_ARG2);
+    else if (sexp_flonump(_ARG1) && sexp_fixnump(_ARG2))
+      i = sexp_flonum_value(_ARG1) == (double)sexp_unbox_fixnum(_ARG2);
+    else if (sexp_fixnump(_ARG1) && sexp_flonump(_ARG2))
+      i = (double)sexp_unbox_fixnum(_ARG1) == sexp_flonum_value(_ARG2);
 #endif
     else sexp_raise("=: not a number", sexp_list2(ctx, _ARG1, _ARG2));
     _ARG2 = sexp_make_boolean(i);
@@ -1794,8 +1791,8 @@ sexp sexp_vm (sexp ctx, sexp proc) {
     top--;
     break;
   case OP_FIX2FLO:
-    if (sexp_integerp(_ARG1))
-      _ARG1 = sexp_integer_to_flonum(ctx, _ARG1);
+    if (sexp_fixnump(_ARG1))
+      _ARG1 = sexp_fixnum_to_flonum(ctx, _ARG1);
 #if USE_BIGNUMS
     else if (sexp_bignump(_ARG1))
       _ARG1 = sexp_make_flonum(ctx, sexp_bignum_to_double(_ARG1));
@@ -1811,17 +1808,17 @@ sexp sexp_vm (sexp ctx, sexp proc) {
                  || sexp_flonum_value(_ARG1) < SEXP_MIN_FIXNUM) {
         _ARG1 = sexp_double_to_bignum(ctx, sexp_flonum_value(_ARG1));
       } else {
-        _ARG1 = sexp_make_integer((sexp_sint_t)sexp_flonum_value(_ARG1));
+        _ARG1 = sexp_make_fixnum((sexp_sint_t)sexp_flonum_value(_ARG1));
       }
-    } else if (! sexp_integerp(_ARG1) && ! sexp_bignump(_ARG1)) {
+    } else if (! sexp_fixnump(_ARG1) && ! sexp_bignump(_ARG1)) {
       sexp_raise("inexact->exact: not a number", sexp_list1(ctx, _ARG1));
     }
     break;
   case OP_CHAR2INT:
-    _ARG1 = sexp_make_integer(sexp_unbox_character(_ARG1));
+    _ARG1 = sexp_make_fixnum(sexp_unbox_character(_ARG1));
     break;
   case OP_INT2CHAR:
-    _ARG1 = sexp_make_character(sexp_unbox_integer(_ARG1));
+    _ARG1 = sexp_make_character(sexp_unbox_fixnum(_ARG1));
     break;
   case OP_CHAR_UPCASE:
     _ARG1 = sexp_make_character(toupper(sexp_unbox_character(_ARG1)));
@@ -1875,19 +1872,19 @@ sexp sexp_vm (sexp ctx, sexp proc) {
     _ARG1 = (i == EOF) ? SEXP_EOF : sexp_make_character(i);
     break;
   case OP_RET:
-    i = sexp_unbox_integer(stack[fp]);
+    i = sexp_unbox_fixnum(stack[fp]);
     stack[fp-i] = _ARG1;
     top = fp-i+1;
     self = stack[fp+2];
     bc = sexp_procedure_code(self);
-    ip = sexp_bytecode_data(bc) + sexp_unbox_integer(stack[fp+1]);
+    ip = sexp_bytecode_data(bc) + sexp_unbox_fixnum(stack[fp+1]);
     cp = sexp_procedure_vars(self);
-    fp = sexp_unbox_integer(stack[fp+3]);
+    fp = sexp_unbox_fixnum(stack[fp+3]);
     break;
   case OP_DONE:
     goto end_loop;
   default:
-    sexp_raise("unknown opcode", sexp_list1(ctx, sexp_make_integer(*(ip-1))));
+    sexp_raise("unknown opcode", sexp_list1(ctx, sexp_make_fixnum(*(ip-1))));
   }
   goto loop;
 
@@ -2011,8 +2008,8 @@ sexp sexp_load (sexp ctx, sexp source, sexp env) {
     double d;                             \
     if (sexp_flonump(z))                  \
       d = sexp_flonum_value(z);           \
-    else if (sexp_integerp(z))            \
-      d = (double)sexp_unbox_integer(z);  \
+    else if (sexp_fixnump(z))            \
+      d = (double)sexp_unbox_fixnum(z);  \
     maybe_convert_bignum(z)               \
     else                                  \
       return sexp_type_exception(ctx, "not a number", z); \
@@ -2040,10 +2037,10 @@ static sexp sexp_expt (sexp ctx, sexp x, sexp e) {
   sexp res;
 #if USE_BIGNUMS
   if (sexp_bignump(e)) {
-    if ((x == sexp_make_integer(0)) || (x == sexp_make_integer(-1)))
+    if ((x == sexp_make_fixnum(0)) || (x == sexp_make_fixnum(-1)))
       res = sexp_make_flonum(ctx, pow(0, 0));
-    else if (x == sexp_make_integer(1))
-      res = sexp_make_flonum(ctx, sexp_unbox_integer(x));
+    else if (x == sexp_make_fixnum(1))
+      res = sexp_make_flonum(ctx, sexp_unbox_fixnum(x));
     else if (sexp_flonump(x))
       res = sexp_make_flonum(ctx, pow(sexp_flonum_value(x), sexp_bignum_to_double(e)));
     else
@@ -2052,16 +2049,16 @@ static sexp sexp_expt (sexp ctx, sexp x, sexp e) {
     res = sexp_bignum_expt(ctx, x, e);
   } else {
 #endif
-  if (sexp_integerp(x))
-    x1 = (double)sexp_unbox_integer(x);
+  if (sexp_fixnump(x))
+    x1 = (double)sexp_unbox_fixnum(x);
 #if USE_FLONUMS
   else if (sexp_flonump(x))
     x1 = sexp_flonum_value(x);
 #endif
   else
     return sexp_type_exception(ctx, "not a number", x);
-  if (sexp_integerp(e))
-    e1 = (double)sexp_unbox_integer(e);
+  if (sexp_fixnump(e))
+    e1 = (double)sexp_unbox_fixnum(e);
 #if USE_FLONUMS
   else if (sexp_flonump(e))
     e1 = sexp_flonum_value(e);
@@ -2077,7 +2074,7 @@ static sexp sexp_expt (sexp ctx, sexp x, sexp e) {
       res = sexp_bignum_expt(ctx, sexp_fixnum_to_bignum(ctx, x), e);
   } else
 #endif
-    res = sexp_make_integer((sexp_sint_t)round(f));
+    res = sexp_make_fixnum((sexp_sint_t)round(f));
 #if USE_BIGNUMS
   }
 #endif
@@ -2099,7 +2096,7 @@ static sexp sexp_string_cmp (sexp ctx, sexp str1, sexp str2, sexp ci) {
     diff = strncasecmp(sexp_string_data(str1), sexp_string_data(str2), len);
   if (! diff)
     diff = len1 - len2;
-  return sexp_make_integer(diff);
+  return sexp_make_fixnum(diff);
 }
 
 #ifdef PLAN9
@@ -2193,8 +2190,8 @@ static sexp sexp_make_standard_env (sexp ctx, sexp version) {
   emit(ctx2, OP_DONE);
   tmp = sexp_make_vector(ctx2, 0, SEXP_VOID);
   err_handler = sexp_make_procedure(ctx2,
-                                    sexp_make_integer(0),
-                                    sexp_make_integer(0),
+                                    sexp_make_fixnum(0),
+                                    sexp_make_fixnum(0),
                                     finalize_bytecode(ctx2),
                                     tmp);
   env_define(ctx2, e, the_err_handler_symbol, err_handler);
@@ -2227,15 +2224,15 @@ sexp sexp_env_copy (sexp ctx, sexp to, sexp from, sexp ls) {
 sexp sexp_apply (sexp ctx, sexp proc, sexp args) {
   sexp ls, *stack = sexp_stack_data(sexp_context_stack(ctx));
   sexp_sint_t top = sexp_context_top(ctx), offset;
-  offset = top + sexp_unbox_integer(sexp_length(ctx, args));
+  offset = top + sexp_unbox_fixnum(sexp_length(ctx, args));
   for (ls=args; sexp_pairp(ls); ls=sexp_cdr(ls), top++)
     stack[--offset] = sexp_car(ls);
-  stack[top] = sexp_make_integer(top);
+  stack[top] = sexp_make_fixnum(top);
   top++;
   sexp_context_top(ctx) = top + 3;
-  stack[top++] = sexp_make_integer(0);
+  stack[top++] = sexp_make_fixnum(0);
   stack[top++] = final_resumer;
-  stack[top++] = sexp_make_integer(0);
+  stack[top++] = sexp_make_fixnum(0);
   return sexp_vm(ctx, proc);
 }
 
@@ -2250,7 +2247,7 @@ sexp sexp_compile (sexp ctx, sexp x) {
     generate(ctx, ast);
     res = finalize_bytecode(ctx);
     vec = sexp_make_vector(ctx, 0, SEXP_VOID);
-    res = sexp_make_procedure(ctx, sexp_make_integer(0), sexp_make_integer(0),
+    res = sexp_make_procedure(ctx, sexp_make_fixnum(0), sexp_make_fixnum(0),
                               res, vec);
   }
   sexp_gc_release4(ctx);
@@ -2311,8 +2308,8 @@ void sexp_scheme_init (void) {
     ctx = sexp_make_child_context(ctx, NULL);
     emit(ctx, OP_DONE);
     final_resumer = sexp_make_procedure(ctx,
-                                        sexp_make_integer(0),
-                                        sexp_make_integer(0),
+                                        sexp_make_fixnum(0),
+                                        sexp_make_fixnum(0),
                                         finalize_bytecode(ctx),
                                         sexp_make_vector(ctx, 0, SEXP_VOID));
     sexp_bytecode_name(sexp_procedure_code(final_resumer))
diff --git a/gc.c b/gc.c
index bb50dd39..e9d5577e 100644
--- a/gc.c
+++ b/gc.c
@@ -149,7 +149,7 @@ sexp sexp_sweep (sexp ctx, size_t *sum_freed_ptr) {
     }
   }
   sum_freed_ptr[0] = sum_freed;
-  return sexp_make_integer(max_freed);
+  return sexp_make_fixnum(max_freed);
 }
 
 sexp sexp_gc (sexp ctx, size_t *sum_freed) {
@@ -217,7 +217,7 @@ void* sexp_alloc (sexp ctx, size_t size) {
   size = sexp_heap_align(size);
   res = sexp_try_alloc(ctx, size);
   if (! res) {
-    max_freed = sexp_unbox_integer(sexp_gc(ctx, &sum_freed));
+    max_freed = sexp_unbox_fixnum(sexp_gc(ctx, &sum_freed));
     h = sexp_heap_last(heap);
     if (((max_freed < size)
          || ((h->size - sum_freed) < (h->size*(1 - SEXP_GROW_HEAP_RATIO))))
diff --git a/include/chibi/sexp.h b/include/chibi/sexp.h
index a3a00dcb..3b0c9183 100644
--- a/include/chibi/sexp.h
+++ b/include/chibi/sexp.h
@@ -334,7 +334,7 @@ void *sexp_realloc(sexp ctx, sexp x, size_t size);
 
 #define sexp_nullp(x)    ((x) == SEXP_NULL)
 #define sexp_pointerp(x) (((sexp_uint_t)(x) & SEXP_FIXNUM_MASK) == SEXP_POINTER_TAG)
-#define sexp_integerp(x) (((sexp_uint_t)(x) & SEXP_FIXNUM_MASK) == SEXP_FIXNUM_TAG)
+#define sexp_fixnump(x)  (((sexp_uint_t)(x) & SEXP_FIXNUM_MASK) == SEXP_FIXNUM_TAG)
 #define sexp_isymbolp(x) (((sexp_uint_t)(x) & SEXP_IMMEDIATE_MASK) == SEXP_ISYMBOL_TAG)
 #define sexp_charp(x)    (((sexp_uint_t)(x) & SEXP_EXTENDED_MASK) == SEXP_CHAR_TAG)
 #define sexp_booleanp(x) (((x) == SEXP_TRUE) || ((x) == SEXP_FALSE))
@@ -398,18 +398,26 @@ sexp sexp_make_flonum(sexp ctx, double f);
 #define sexp_make_boolean(x) ((x) ? SEXP_TRUE : SEXP_FALSE)
 #define sexp_unbox_boolean(x) (((x) == SEXP_FALSE) ? 0 : 1)
 
-#define sexp_make_integer(n)    ((sexp) ((((sexp_sint_t)(n))<<SEXP_FIXNUM_BITS) + SEXP_FIXNUM_TAG))
-#define sexp_unbox_integer(n)   (((sexp_sint_t)(n))>>SEXP_FIXNUM_BITS)
+#define sexp_make_fixnum(n)    ((sexp) ((((sexp_sint_t)(n))<<SEXP_FIXNUM_BITS) + SEXP_FIXNUM_TAG))
+#define sexp_unbox_fixnum(n)   (((sexp_sint_t)(n))>>SEXP_FIXNUM_BITS)
 
 #define sexp_make_character(n)  ((sexp) ((((sexp_sint_t)(n))<<SEXP_EXTENDED_BITS) + SEXP_CHAR_TAG))
 #define sexp_unbox_character(n) ((int) (((sexp_sint_t)(n))>>SEXP_EXTENDED_BITS))
 
-#define sexp_integer_to_double(x) ((double)sexp_unbox_integer(x))
+#define sexp_fixnum_to_double(x) ((double)sexp_unbox_fixnum(x))
+
+#if USE_BIGNUMS
+SEXP_API sexp sexp_make_integer(sexp ctx, sexp_sint_t x);
+#define sexp_integerp(x) (sexp_fixnump(x) || sexp_bignump(x))
+#else
+#define sexp_make_integer(ctx, x) sexp_make_fixnum(x)
+#define sexp_integerp sexp_fixnump
+#endif
 
 #if USE_FLONUMS
-#define sexp_integer_to_flonum(ctx, x) (sexp_make_flonum(ctx, sexp_unbox_integer(x)))
+#define sexp_fixnum_to_flonum(ctx, x) (sexp_make_flonum(ctx, sexp_unbox_fixnum(x)))
 #else
-#define sexp_integer_to_flonum(ctx, x) (x)
+#define sexp_fixnum_to_flonum(ctx, x) (x)
 #endif
 
 /*************************** field accessors **************************/
@@ -417,20 +425,20 @@ sexp sexp_make_flonum(sexp ctx, double f);
 #define sexp_vector_length(x) ((x)->value.vector.length)
 #define sexp_vector_data(x)   ((x)->value.vector.data)
 
-#define sexp_vector_ref(x,i)   (sexp_vector_data(x)[sexp_unbox_integer(i)])
-#define sexp_vector_set(x,i,v) (sexp_vector_data(x)[sexp_unbox_integer(i)]=(v))
+#define sexp_vector_ref(x,i)   (sexp_vector_data(x)[sexp_unbox_fixnum(i)])
+#define sexp_vector_set(x,i,v) (sexp_vector_data(x)[sexp_unbox_fixnum(i)]=(v))
 
 #define sexp_procedure_num_args(x) ((x)->value.procedure.num_args)
 #define sexp_procedure_flags(x) ((x)->value.procedure.flags)
-#define sexp_procedure_variadic_p(x) (sexp_unbox_integer(sexp_procedure_flags(x)) & 1)
+#define sexp_procedure_variadic_p(x) (sexp_unbox_fixnum(sexp_procedure_flags(x)) & 1)
 #define sexp_procedure_code(x) ((x)->value.procedure.bc)
 #define sexp_procedure_vars(x) ((x)->value.procedure.vars)
 
 #define sexp_string_length(x) ((x)->value.string.length)
 #define sexp_string_data(x)   ((x)->value.string.data)
 
-#define sexp_string_ref(x, i) (sexp_make_character(sexp_string_data(x)[sexp_unbox_integer(i)]))
-#define sexp_string_set(x, i, v) (sexp_string_data(x)[sexp_unbox_integer(i)] = sexp_unbox_character(v))
+#define sexp_string_ref(x, i) (sexp_make_character(sexp_string_data(x)[sexp_unbox_fixnum(i)]))
+#define sexp_string_set(x, i, v) (sexp_string_data(x)[sexp_unbox_fixnum(i)] = sexp_unbox_character(v))
 
 #define sexp_symbol_string(x)  ((x)->value.symbol.string)
 
@@ -552,10 +560,10 @@ sexp sexp_make_flonum(sexp ctx, double f);
 #define sexp_fx_add(a, b) ((sexp)(((sexp_sint_t)a)+((sexp_sint_t)b)-SEXP_FIXNUM_TAG))
 #define sexp_fx_sub(a, b) ((sexp)(((sexp_sint_t)a)-((sexp_sint_t)b)+SEXP_FIXNUM_TAG))
 #define sexp_fx_mul(a, b) ((sexp)((((((sexp_sint_t)a)-SEXP_FIXNUM_TAG)*(((sexp_sint_t)b)>>SEXP_FIXNUM_BITS))+SEXP_FIXNUM_TAG)))
-#define sexp_fx_div(a, b) (sexp_make_integer(sexp_unbox_integer(a) / sexp_unbox_integer(b)))
-#define sexp_fx_rem(a, b) (sexp_make_integer(sexp_unbox_integer(a) % sexp_unbox_integer(b)))
+#define sexp_fx_div(a, b) (sexp_make_fixnum(sexp_unbox_fixnum(a) / sexp_unbox_fixnum(b)))
+#define sexp_fx_rem(a, b) (sexp_make_fixnum(sexp_unbox_fixnum(a) % sexp_unbox_fixnum(b)))
 #define sexp_fx_sign(a)   (+1 | (((sexp_sint_t)(a)) >> (sizeof(int)*8 - 1)))
-#define sexp_fx_neg(a)    (sexp_make_integer(-(sexp_unbox_integer(a))))
+#define sexp_fx_neg(a)    (sexp_make_fixnum(-(sexp_unbox_fixnum(a))))
 #define sexp_fx_abs(a)    ((((sexp_sint_t)a) < 0) ? sexp_fx_neg(a) : a)
 
 #define sexp_fp_add(x,a,b) (sexp_make_flonum(x, sexp_flonum_value(a) + sexp_flonum_value(b)))
diff --git a/opcodes.c b/opcodes.c
index fc2277b4..8f29fca7 100644
--- a/opcodes.c
+++ b/opcodes.c
@@ -30,8 +30,8 @@ _OP(OPC_GENERIC, OP_CHAR2INT, 1, 0, SEXP_CHAR, 0, 0, "char->integer", 0, NULL),
 _OP(OPC_GENERIC, OP_INT2CHAR, 1, 0, SEXP_FIXNUM, 0, 0, "integer->char", 0, NULL),
 _OP(OPC_GENERIC, OP_CHAR_UPCASE, 1, 0, SEXP_CHAR, 0, 0, "char-upcase", 0, NULL),
 _OP(OPC_GENERIC, OP_CHAR_DOWNCASE, 1, 0, SEXP_CHAR, 0, 0, "char-downcase", 0, NULL),
-_OP(OPC_ARITHMETIC,     OP_ADD, 0, 1, SEXP_FIXNUM, 0, 0, "+", sexp_make_integer(0), NULL),
-_OP(OPC_ARITHMETIC,     OP_MUL, 0, 1, SEXP_FIXNUM, 0, 0, "*", sexp_make_integer(1), NULL),
+_OP(OPC_ARITHMETIC,     OP_ADD, 0, 1, SEXP_FIXNUM, 0, 0, "+", sexp_make_fixnum(0), NULL),
+_OP(OPC_ARITHMETIC,     OP_MUL, 0, 1, SEXP_FIXNUM, 0, 0, "*", sexp_make_fixnum(1), NULL),
 _OP(OPC_ARITHMETIC_INV, OP_SUB, 0, 1, SEXP_FIXNUM, 0, OP_NEGATIVE, "-", 0, NULL),
 _OP(OPC_ARITHMETIC_INV, OP_DIV, 0, 1, SEXP_FIXNUM, 0, OP_INVERSE, "/", 0, NULL),
 _OP(OPC_ARITHMETIC,     OP_QUOTIENT, 2, 0, SEXP_FIXNUM, SEXP_FIXNUM, 0, "quotient", 0, NULL),
@@ -50,14 +50,14 @@ _OP(OPC_TYPE_PREDICATE, OP_EOFP,  1, 0, 0, 0, 0, "eof-object?", NULL, 0),
 _OP(OPC_TYPE_PREDICATE, OP_SYMBOLP,  1, 0, 0, 0, 0, "symbol?", NULL, 0),
 _OP(OPC_TYPE_PREDICATE, OP_CHARP,  1, 0, 0, 0, 0, "char?", NULL, 0),
 _OP(OPC_TYPE_PREDICATE, OP_INTEGERP,  1, 0, 0, 0, 0, "fixnum?", NULL, 0),
-_OP(OPC_TYPE_PREDICATE, OP_TYPEP,  1, 0, 0, 0, 0, "pair?", sexp_make_integer(SEXP_PAIR), 0),
-_OP(OPC_TYPE_PREDICATE, OP_TYPEP,  1, 0, 0, 0, 0, "string?", sexp_make_integer(SEXP_STRING), 0),
-_OP(OPC_TYPE_PREDICATE, OP_TYPEP,  1, 0, 0, 0, 0, "vector?", sexp_make_integer(SEXP_VECTOR), 0),
-_OP(OPC_TYPE_PREDICATE, OP_TYPEP,  1, 0, 0, 0, 0, "flonum?", sexp_make_integer(SEXP_FLONUM), 0),
-_OP(OPC_TYPE_PREDICATE, OP_TYPEP,  1, 0, 0, 0, 0, "closure?", sexp_make_integer(SEXP_PROCEDURE), 0),
-_OP(OPC_TYPE_PREDICATE, OP_TYPEP,  1, 0, 0, 0, 0, "opcode?", sexp_make_integer(SEXP_OPCODE), 0),
-_OP(OPC_TYPE_PREDICATE, OP_TYPEP,  1, 0, 0, 0, 0, "input-port?", sexp_make_integer(SEXP_IPORT), 0),
-_OP(OPC_TYPE_PREDICATE, OP_TYPEP,  1, 0, 0, 0, 0, "output-port?", sexp_make_integer(SEXP_OPORT), 0),
+_OP(OPC_TYPE_PREDICATE, OP_TYPEP,  1, 0, 0, 0, 0, "pair?", sexp_make_fixnum(SEXP_PAIR), 0),
+_OP(OPC_TYPE_PREDICATE, OP_TYPEP,  1, 0, 0, 0, 0, "string?", sexp_make_fixnum(SEXP_STRING), 0),
+_OP(OPC_TYPE_PREDICATE, OP_TYPEP,  1, 0, 0, 0, 0, "vector?", sexp_make_fixnum(SEXP_VECTOR), 0),
+_OP(OPC_TYPE_PREDICATE, OP_TYPEP,  1, 0, 0, 0, 0, "flonum?", sexp_make_fixnum(SEXP_FLONUM), 0),
+_OP(OPC_TYPE_PREDICATE, OP_TYPEP,  1, 0, 0, 0, 0, "closure?", sexp_make_fixnum(SEXP_PROCEDURE), 0),
+_OP(OPC_TYPE_PREDICATE, OP_TYPEP,  1, 0, 0, 0, 0, "opcode?", sexp_make_fixnum(SEXP_OPCODE), 0),
+_OP(OPC_TYPE_PREDICATE, OP_TYPEP,  1, 0, 0, 0, 0, "input-port?", sexp_make_fixnum(SEXP_IPORT), 0),
+_OP(OPC_TYPE_PREDICATE, OP_TYPEP,  1, 0, 0, 0, 0, "output-port?", sexp_make_fixnum(SEXP_OPORT), 0),
 _OP(OPC_GENERIC, OP_APPLY1, 2, 0, SEXP_PROCEDURE, SEXP_PAIR, 0, "apply1", 0, NULL),
 _OP(OPC_GENERIC, OP_CALLCC, 1, SEXP_PROCEDURE, 0, 0, 0, "call-with-current-continuation", 0, NULL),
 _OP(OPC_GENERIC, OP_RAISE, 1, SEXP_STRING, 0, 0, 0, "raise", 0, NULL),
diff --git a/opt/bignum.c b/opt/bignum.c
index e4e4f8ea..4ffafa1e 100644
--- a/opt/bignum.c
+++ b/opt/bignum.c
@@ -7,7 +7,7 @@
 #define sexp_negate(x)                                  \
   if (sexp_bignump(x))                                  \
     sexp_bignum_sign(x) = -sexp_bignum_sign(x);         \
-  else if (sexp_integerp(x))                            \
+  else if (sexp_fixnump(x))                            \
     x = sexp_fx_neg(x);
 
 sexp sexp_make_bignum (sexp ctx, sexp_uint_t len) {
@@ -20,11 +20,23 @@ sexp sexp_make_bignum (sexp ctx, sexp_uint_t len) {
 
 sexp sexp_fixnum_to_bignum (sexp ctx, sexp a) {
   sexp res = sexp_make_bignum(ctx, 1);
-  sexp_bignum_data(res)[0] = sexp_unbox_integer(sexp_fx_abs(a));
+  sexp_bignum_data(res)[0] = sexp_unbox_fixnum(sexp_fx_abs(a));
   sexp_bignum_sign(res) = sexp_fx_sign(a);
   return res;
 }
 
+sexp sexp_make_integer (sexp ctx, sexp_sint_t x) {
+  sexp res;
+  if ((SEXP_MIN_FIXNUM < x) && (x < SEXP_MAX_FIXNUM)) {
+    res = sexp_make_fixnum(x);
+  } else {
+    res = sexp_make_bignum(ctx, 1);
+    sexp_bignum_sign(res) = (x < 0 ? -1 : 1);
+    sexp_bignum_data(res)[0] = x * sexp_bignum_sign(res);
+  }
+  return res;
+}
+
 #define double_trunc_10s_digit(f) (trunc((f)/10.0)*10.0)
 #define double_10s_digit(f) ((f)-double_trunc_10s_digit(f))
 
@@ -32,8 +44,8 @@ sexp sexp_double_to_bignum (sexp ctx, double f) {
   int sign;
   sexp_gc_var3(res, scale, tmp);
   sexp_gc_preserve3(ctx, res, scale, tmp);
-  res = sexp_fixnum_to_bignum(ctx, sexp_make_integer(0));
-  scale = sexp_fixnum_to_bignum(ctx, sexp_make_integer(1));
+  res = sexp_fixnum_to_bignum(ctx, sexp_make_fixnum(0));
+  scale = sexp_fixnum_to_bignum(ctx, sexp_make_fixnum(1));
   sign = (f < 0 ? -1 : 1);
   for (f=fabs(f); f >= 1.0; f=trunc(f/10)) {
     tmp = sexp_bignum_fxmul(ctx, NULL, scale, double_10s_digit(f), 0);
@@ -105,7 +117,7 @@ sexp sexp_bignum_normalize (sexp a) {
   if ((data[0] > SEXP_MAX_FIXNUM)
       && ! ((sexp_bignum_sign(a) == -1) && (data[0] == SEXP_MAX_FIXNUM+1)))
     return a;
-  return sexp_make_integer((sexp_sint_t)data[0] * sexp_bignum_sign(a));
+  return sexp_make_fixnum((sexp_sint_t)data[0] * sexp_bignum_sign(a));
 }
 
 double sexp_bignum_to_double (sexp a) {
@@ -226,7 +238,7 @@ sexp sexp_write_bignum (sexp ctx, sexp a, sexp out, sexp_uint_t base) {
   sexp_bignum_sign(b) = 1;
   i = str_len = (sexp_bignum_length(b)*sizeof(sexp_uint_t)*8 + lg_base - 1)
     / lg_base + 1;
-  str = sexp_make_string(ctx, sexp_make_integer(str_len),
+  str = sexp_make_string(ctx, sexp_make_fixnum(str_len),
                          sexp_make_character(' '));
   data = sexp_string_data(str);
   while (! sexp_bignum_zerop(b))
@@ -247,9 +259,9 @@ sexp sexp_bignum_add_fixnum (sexp ctx, sexp a, sexp b) {
   sexp_gc_preserve1(ctx, c);
   c = sexp_copy_bignum(ctx, NULL, a, 0);
   if (sexp_bignum_sign(c) == sexp_fx_sign(b))
-    c = sexp_bignum_fxadd(ctx, c, sexp_unbox_integer(sexp_fx_abs(b)));
+    c = sexp_bignum_fxadd(ctx, c, sexp_unbox_fixnum(sexp_fx_abs(b)));
   else
-    c = sexp_bignum_fxsub(ctx, c, sexp_unbox_integer(sexp_fx_abs(b)));
+    c = sexp_bignum_fxsub(ctx, c, sexp_unbox_fixnum(sexp_fx_abs(b)));
   sexp_gc_release1(ctx);
   return c;
 }
@@ -360,7 +372,7 @@ static sexp quot_step (sexp ctx, sexp *rem, sexp a, sexp b, sexp k, sexp i) {
   sexp_gc_var5(x, prod, diff, k2, i2);
   if (sexp_bignum_compare(k, a) > 0) {
     *rem = a;
-    return sexp_fixnum_to_bignum(ctx, sexp_make_integer(0));
+    return sexp_fixnum_to_bignum(ctx, sexp_make_fixnum(0));
   }
   sexp_gc_preserve5(ctx, x, prod, diff, k2, i2);
   k2 = sexp_bignum_double(ctx, k);
@@ -388,7 +400,7 @@ sexp sexp_bignum_quot_rem (sexp ctx, sexp *rem, sexp a, sexp b) {
   b1 = sexp_copy_bignum(ctx, NULL, b, 0);
   sexp_bignum_sign(b1) = 1;
   k = sexp_copy_bignum(ctx, NULL, b1, 0);
-  i = sexp_fixnum_to_bignum(ctx, sexp_make_integer(1));
+  i = sexp_fixnum_to_bignum(ctx, sexp_make_fixnum(1));
   res = quot_step(ctx, rem, a1, b1, k, i);
   sexp_bignum_sign(res) = sexp_bignum_sign(a) * sexp_bignum_sign(b);
   if (sexp_bignum_sign(a) < 0) {
@@ -414,10 +426,10 @@ sexp sexp_bignum_remainder (sexp ctx, sexp a, sexp b) {
 }
 
 sexp sexp_bignum_expt (sexp ctx, sexp a, sexp b) {
-  sexp_sint_t e = sexp_unbox_integer(sexp_fx_abs(b));
+  sexp_sint_t e = sexp_unbox_fixnum(sexp_fx_abs(b));
   sexp_gc_var2(res, acc);
   sexp_gc_preserve2(ctx, res, acc);
-  res = sexp_fixnum_to_bignum(ctx, sexp_make_integer(1));
+  res = sexp_fixnum_to_bignum(ctx, sexp_make_fixnum(1));
   acc = sexp_copy_bignum(ctx, NULL, a, 0);
   for (; e; e>>=1, acc=sexp_bignum_mul(ctx, NULL, acc, acc))
     if (e & 1)
@@ -460,7 +472,7 @@ static int sexp_number_types[SEXP_NUM_TYPES] =
 
 static int sexp_number_type (sexp a) {
   return sexp_pointerp(a) ? sexp_number_types[sexp_pointer_tag(a)]
-    : sexp_integerp(a);
+    : sexp_fixnump(a);
 }
 
 sexp sexp_add (sexp ctx, sexp a, sexp b) {
@@ -476,7 +488,7 @@ sexp sexp_add (sexp ctx, sexp a, sexp b) {
     r = sexp_fx_add(a, b);      /* XXXX check overflow */
     break;
   case SEXP_NUM_FIX_FLO:
-    r = sexp_make_flonum(ctx, sexp_integer_to_double(a)+sexp_flonum_value(b));
+    r = sexp_make_flonum(ctx, sexp_fixnum_to_double(a)+sexp_flonum_value(b));
     break;
   case SEXP_NUM_FIX_BIG:
     r = sexp_bignum_normalize(sexp_bignum_add_fixnum(ctx, b, a));
@@ -509,7 +521,7 @@ sexp sexp_sub (sexp ctx, sexp a, sexp b) {
     r = sexp_fx_sub(a, b);      /* XXXX check overflow */
     break;
   case SEXP_NUM_FIX_FLO:
-    r = sexp_make_flonum(ctx, sexp_integer_to_double(a)-sexp_flonum_value(b));
+    r = sexp_make_flonum(ctx, sexp_fixnum_to_double(a)-sexp_flonum_value(b));
     break;
   case SEXP_NUM_FIX_BIG:
     r = sexp_bignum_sub(ctx, NULL, b, sexp_fixnum_to_bignum(ctx, a));
@@ -517,7 +529,7 @@ sexp sexp_sub (sexp ctx, sexp a, sexp b) {
     r = sexp_bignum_normalize(r);
     break;
   case SEXP_NUM_FLO_FIX:
-    r = sexp_make_flonum(ctx, sexp_integer_to_double(b)+sexp_flonum_value(a));
+    r = sexp_make_flonum(ctx, sexp_fixnum_to_double(b)+sexp_flonum_value(a));
     break;
   case SEXP_NUM_FLO_FLO:
     r = sexp_fp_sub(ctx, a, b);
@@ -550,10 +562,10 @@ sexp sexp_mul (sexp ctx, sexp a, sexp b) {
     r = sexp_fx_mul(a, b);
     break;
   case SEXP_NUM_FIX_FLO:
-    r = sexp_make_flonum(ctx, sexp_integer_to_double(a)*sexp_flonum_value(b));
+    r = sexp_make_flonum(ctx, sexp_fixnum_to_double(a)*sexp_flonum_value(b));
     break;
   case SEXP_NUM_FIX_BIG:
-    r = sexp_bignum_fxmul(ctx, NULL, b, sexp_unbox_integer(sexp_fx_abs(a)), 0);
+    r = sexp_bignum_fxmul(ctx, NULL, b, sexp_unbox_fixnum(sexp_fx_abs(a)), 0);
     sexp_bignum_sign(r) = sexp_fx_sign(a) * sexp_bignum_sign(b);
     break;
   case SEXP_NUM_FLO_FLO:
@@ -582,18 +594,18 @@ sexp sexp_div (sexp ctx, sexp a, sexp b) {
     r = sexp_type_exception(ctx, "/: not a number", b);
     break;
   case SEXP_NUM_FIX_FIX:
-    f = sexp_integer_to_double(a) / sexp_integer_to_double(b);
-    r = ((f == trunc(f)) ? sexp_make_integer((sexp_sint_t)f)
+    f = sexp_fixnum_to_double(a) / sexp_fixnum_to_double(b);
+    r = ((f == trunc(f)) ? sexp_make_fixnum((sexp_sint_t)f)
          : sexp_make_flonum(ctx, f));
     break;
   case SEXP_NUM_FIX_FLO:
-    r = sexp_make_flonum(ctx, sexp_integer_to_double(a)/sexp_flonum_value(b));
+    r = sexp_make_flonum(ctx, sexp_fixnum_to_double(a)/sexp_flonum_value(b));
     break;
   case SEXP_NUM_FIX_BIG:
-    r = sexp_make_flonum(ctx, sexp_integer_to_double(a)/sexp_bignum_to_double(b));
+    r = sexp_make_flonum(ctx, sexp_fixnum_to_double(a)/sexp_bignum_to_double(b));
     break;
   case SEXP_NUM_FLO_FIX:
-    r = sexp_make_flonum(ctx, sexp_integer_to_double(b)/sexp_flonum_value(a));
+    r = sexp_make_flonum(ctx, sexp_fixnum_to_double(b)/sexp_flonum_value(a));
     break;
   case SEXP_NUM_FLO_FLO:
     r = sexp_fp_div(ctx, a, b);
@@ -606,9 +618,9 @@ sexp sexp_div (sexp ctx, sexp a, sexp b) {
     /* ... FALLTHROUGH ... */
   case SEXP_NUM_BIG_BIG:
     r = sexp_bignum_quot_rem(ctx, &rem, a, b);
-    if (sexp_bignum_normalize(rem) != sexp_make_integer(0))
+    if (sexp_bignum_normalize(rem) != sexp_make_fixnum(0))
       r = sexp_make_flonum(ctx, sexp_bignum_to_double(a)
-                           / sexp_integer_to_double(b));
+                           / sexp_fixnum_to_double(b));
     else
       r = sexp_bignum_normalize(r);
     break;
@@ -640,7 +652,7 @@ sexp sexp_quotient (sexp ctx, sexp a, sexp b) {
     r = sexp_fx_div(a, b);
     break;
   case SEXP_NUM_FIX_BIG:
-    r = sexp_make_integer(0);
+    r = sexp_make_fixnum(0);
     break;
   case SEXP_NUM_BIG_FIX:
     b = sexp_fixnum_to_bignum(ctx, b);
@@ -699,25 +711,25 @@ sexp sexp_compare (sexp ctx, sexp a, sexp b) {
       r = sexp_type_exception(ctx, "compare: not a number", a);
       break;
     case SEXP_NUM_FIX_FIX:
-      r = sexp_make_integer(sexp_unbox_integer(a) - sexp_unbox_integer(b));
+      r = sexp_make_fixnum(sexp_unbox_fixnum(a) - sexp_unbox_fixnum(b));
       break;
     case SEXP_NUM_FIX_FLO:
-      f = sexp_integer_to_double(a) - sexp_flonum_value(b);
-      r = sexp_make_integer(f > 0.0 ? 1 : f == 0.0 ? 0 : -1);
+      f = sexp_fixnum_to_double(a) - sexp_flonum_value(b);
+      r = sexp_make_fixnum(f > 0.0 ? 1 : f == 0.0 ? 0 : -1);
       break;
     case SEXP_NUM_FIX_BIG:
-      r = sexp_make_integer(-1);
+      r = sexp_make_fixnum(-1);
       break;
     case SEXP_NUM_FLO_FLO:
       f = sexp_flonum_value(a) - sexp_flonum_value(b);
-      r = sexp_make_integer(f > 0.0 ? 1 : f == 0.0 ? 0 : -1);
+      r = sexp_make_fixnum(f > 0.0 ? 1 : f == 0.0 ? 0 : -1);
       break;
     case SEXP_NUM_FLO_BIG:
       f = sexp_flonum_value(a) - sexp_bignum_to_double(b);
-      r = sexp_make_integer(f > 0.0 ? 1 : f == 0.0 ? 0 : -1);
+      r = sexp_make_fixnum(f > 0.0 ? 1 : f == 0.0 ? 0 : -1);
       break;
     case SEXP_NUM_BIG_BIG:
-      r = sexp_make_integer(sexp_bignum_compare(a, b));
+      r = sexp_make_fixnum(sexp_bignum_compare(a, b));
       break;
     }
   }
diff --git a/sexp.c b/sexp.c
index e1f9c233..946a1319 100644
--- a/sexp.c
+++ b/sexp.c
@@ -169,8 +169,8 @@ sexp sexp_print_exception (sexp ctx, sexp exn, sexp out) {
     }
     if (sexp_pairp(sexp_exception_source(exn))) {
       ls = sexp_exception_source(exn);
-      if (sexp_integerp(sexp_cdr(ls))
-          && (sexp_cdr(ls) >= sexp_make_integer(0))) {
+      if (sexp_fixnump(sexp_cdr(ls))
+          && (sexp_cdr(ls) >= sexp_make_fixnum(0))) {
         sexp_write_string(ctx, " on line ", out);
         sexp_write(ctx, sexp_cdr(ls), out);
       }
@@ -218,7 +218,7 @@ static sexp sexp_read_error (sexp ctx, char *msg, sexp irritants, sexp port) {
   sexp_gc_var3(name, str, irr);
   sexp_gc_preserve3(ctx, name, str, irr);
   name = (sexp_port_name(port) ? sexp_port_name(port) : SEXP_FALSE);
-  name = sexp_cons(ctx, name, sexp_make_integer(sexp_port_line(port)));
+  name = sexp_cons(ctx, name, sexp_make_fixnum(sexp_port_line(port)));
   str = sexp_c_string(ctx, msg, -1);
   irr = ((sexp_pairp(irritants) || sexp_nullp(irritants))
          ? irritants : sexp_list1(ctx, irritants));
@@ -320,7 +320,7 @@ sexp sexp_length (sexp ctx, sexp ls) {
   sexp_uint_t res=0;
   for ( ; sexp_pairp(ls); res++, ls=sexp_cdr(ls))
     ;
-  return sexp_make_integer(res);
+  return sexp_make_fixnum(res);
 }
 
 sexp sexp_equalp (sexp ctx, sexp a, sexp b) {
@@ -334,17 +334,17 @@ sexp sexp_equalp (sexp ctx, sexp a, sexp b) {
     return
       sexp_make_boolean((a == b)
                         || (sexp_flonump(a)
-                            && sexp_make_integer(sexp_flonum_value(a)) == b)
+                            && sexp_make_fixnum(sexp_flonum_value(a)) == b)
                         || (sexp_flonump(b)
-                            && sexp_make_integer(sexp_flonum_value(b)) == a));
+                            && sexp_make_fixnum(sexp_flonum_value(b)) == a));
 #else
   if (! sexp_pointerp(a))
-    return sexp_make_boolean(sexp_integerp(a) && sexp_pointerp(b)
-                             && (sexp_unbox_integer(a)
+    return sexp_make_boolean(sexp_fixnump(a) && sexp_pointerp(b)
+                             && (sexp_unbox_fixnum(a)
                                  == sexp_flonum_value(b)));
   else if (! sexp_pointerp(b))
-    return sexp_make_boolean(sexp_integerp(b) && sexp_pointerp(a)
-                             && (sexp_unbox_integer(b)
+    return sexp_make_boolean(sexp_fixnump(b) && sexp_pointerp(a)
+                             && (sexp_unbox_fixnum(b)
                                  == sexp_flonum_value(a)));
 #endif
   if (sexp_pointer_tag(a) != sexp_pointer_tag(b))
@@ -395,9 +395,9 @@ sexp sexp_make_flonum(sexp ctx, double f) {
 #endif
 
 sexp sexp_make_string(sexp ctx, sexp len, sexp ch) {
-  sexp_sint_t clen = sexp_unbox_integer(len);
+  sexp_sint_t clen = sexp_unbox_fixnum(len);
   sexp s;
-  if (! sexp_integerp(len)) return sexp_type_exception(ctx, "bad length", len);
+  if (! sexp_fixnump(len)) return sexp_type_exception(ctx, "bad length", len);
   if (clen < 0) return sexp_type_exception(ctx, "negative length", len);
   s = sexp_alloc_atomic(ctx, sexp_sizeof(string)+clen+1);
   sexp_pointer_tag(s) = SEXP_STRING;
@@ -410,7 +410,7 @@ sexp sexp_make_string(sexp ctx, sexp len, sexp ch) {
 
 sexp sexp_c_string(sexp ctx, char *str, sexp_sint_t slen) {
   sexp_sint_t len = ((slen >= 0) ? slen : strlen(str));
-  sexp s = sexp_make_string(ctx, sexp_make_integer(len), SEXP_VOID);
+  sexp s = sexp_make_string(ctx, sexp_make_fixnum(len), SEXP_VOID);
   memcpy(sexp_string_data(s), str, len);
   sexp_string_data(s)[len] = '\0';
   return s;
@@ -420,21 +420,21 @@ sexp sexp_substring (sexp ctx, sexp str, sexp start, sexp end) {
   sexp res;
   if (! sexp_stringp(str))
     return sexp_type_exception(ctx, "not a string", str);
-  if (! sexp_integerp(start))
+  if (! sexp_fixnump(start))
     return sexp_type_exception(ctx, "not a number", start);
   if (sexp_not(end))
-    end = sexp_make_integer(sexp_string_length(str));
-  if (! sexp_integerp(end))
+    end = sexp_make_fixnum(sexp_string_length(str));
+  if (! sexp_fixnump(end))
     return sexp_type_exception(ctx, "not a number", end);
-  if ((sexp_unbox_integer(start) < 0)
-      || (sexp_unbox_integer(start) > sexp_string_length(str))
-      || (sexp_unbox_integer(end) < 0)
-      || (sexp_unbox_integer(end) > sexp_string_length(str))
+  if ((sexp_unbox_fixnum(start) < 0)
+      || (sexp_unbox_fixnum(start) > sexp_string_length(str))
+      || (sexp_unbox_fixnum(end) < 0)
+      || (sexp_unbox_fixnum(end) > sexp_string_length(str))
       || (end < start))
     return sexp_range_exception(ctx, str, start, end);
   res = sexp_make_string(ctx, sexp_fx_sub(end, start), SEXP_VOID);
   memcpy(sexp_string_data(res),
-         sexp_string_data(str)+sexp_unbox_integer(start),
+         sexp_string_data(str)+sexp_unbox_fixnum(start),
          sexp_string_length(res));
   sexp_string_data(res)[sexp_string_length(res)] = '\0';
   return res;
@@ -449,7 +449,7 @@ sexp sexp_string_concatenate (sexp ctx, sexp str_ls) {
       return sexp_type_exception(ctx, "not a string", sexp_car(ls));
     else
       len += sexp_string_length(sexp_car(ls));
-  res = sexp_make_string(ctx, sexp_make_integer(len), SEXP_VOID);
+  res = sexp_make_string(ctx, sexp_make_fixnum(len), SEXP_VOID);
   p = sexp_string_data(res);
   for (ls=str_ls; sexp_pairp(ls); ls=sexp_cdr(ls)) {
     len = sexp_string_length(sexp_car(ls));
@@ -519,7 +519,7 @@ sexp sexp_string_to_symbol (sexp ctx, sexp str) {
 
 sexp sexp_make_vector(sexp ctx, sexp len, sexp dflt) {
   sexp v, *x;
-  int i, clen = sexp_unbox_integer(len);
+  int i, clen = sexp_unbox_fixnum(len);
   if (! clen) return the_empty_vector;
   v = sexp_alloc_tagged(ctx, sexp_sizeof(vector) + clen*sizeof(sexp),
                         SEXP_VECTOR);
@@ -557,39 +557,39 @@ sexp sexp_make_cpointer (sexp ctx, void *value) {
 
 #if SEXP_BSD
 
-#define sexp_stream_ctx(vec) sexp_vector_ref((sexp)vec, sexp_make_integer(0))
-#define sexp_stream_buf(vec) sexp_vector_ref((sexp)vec, sexp_make_integer(1))
-#define sexp_stream_size(vec) sexp_vector_ref((sexp)vec, sexp_make_integer(2))
-#define sexp_stream_pos(vec) sexp_vector_ref((sexp)vec, sexp_make_integer(3))
+#define sexp_stream_ctx(vec) sexp_vector_ref((sexp)vec, sexp_make_fixnum(0))
+#define sexp_stream_buf(vec) sexp_vector_ref((sexp)vec, sexp_make_fixnum(1))
+#define sexp_stream_size(vec) sexp_vector_ref((sexp)vec, sexp_make_fixnum(2))
+#define sexp_stream_pos(vec) sexp_vector_ref((sexp)vec, sexp_make_fixnum(3))
 
 int sstream_read (void *vec, char *dst, int n) {
-  sexp_uint_t len = sexp_unbox_integer(sexp_stream_size(vec));
-  sexp_uint_t pos = sexp_unbox_integer(sexp_stream_pos(vec));
+  sexp_uint_t len = sexp_unbox_fixnum(sexp_stream_size(vec));
+  sexp_uint_t pos = sexp_unbox_fixnum(sexp_stream_pos(vec));
   if (pos >= len) return 0;
   if (n > (len - pos)) n = (len - pos);
   memcpy(dst, sexp_string_data(sexp_stream_buf(vec))+pos, n);
-  sexp_stream_pos(vec) = sexp_make_integer(n);
+  sexp_stream_pos(vec) = sexp_make_fixnum(n);
   return n;
 }
 
 int sstream_write (void *vec, const char *src, int n) {
   sexp_uint_t len, pos, newpos;
   sexp newbuf;
-  len = sexp_unbox_integer(sexp_stream_size(vec));
-  pos = sexp_unbox_integer(sexp_stream_pos(vec));
+  len = sexp_unbox_fixnum(sexp_stream_size(vec));
+  pos = sexp_unbox_fixnum(sexp_stream_pos(vec));
   newpos = pos+n;
   if (newpos >= len) {
     newbuf = sexp_make_string(sexp_stream_ctx(vec),
-                              sexp_make_integer(newpos*2),
+                              sexp_make_fixnum(newpos*2),
                               SEXP_VOID);
     memcpy(sexp_string_data(newbuf),
            sexp_string_data(sexp_stream_buf(vec)),
            pos);
     sexp_stream_buf(vec) = newbuf;
-    sexp_stream_size(vec) = sexp_make_integer(newpos*2);
+    sexp_stream_size(vec) = sexp_make_fixnum(newpos*2);
   }
   memcpy(sexp_string_data(sexp_stream_buf(vec))+pos, src, n);
-  sexp_stream_pos(vec) = sexp_make_integer(newpos);
+  sexp_stream_pos(vec) = sexp_make_fixnum(newpos);
   return n;
 }
 
@@ -598,11 +598,11 @@ off_t sstream_seek (void *vec, off_t offset, int whence) {
   if (whence == SEEK_SET) {
     pos = offset;
   } else if (whence == SEEK_CUR) {
-    pos = sexp_unbox_integer(sexp_stream_pos(vec)) + offset;
+    pos = sexp_unbox_fixnum(sexp_stream_pos(vec)) + offset;
   } else {                      /* SEEK_END */
-    pos = sexp_unbox_integer(sexp_stream_size(vec)) + offset;
+    pos = sexp_unbox_fixnum(sexp_stream_size(vec)) + offset;
   }
-  sexp_stream_pos(vec) = sexp_make_integer(pos);
+  sexp_stream_pos(vec) = sexp_make_fixnum(pos);
   return pos;
 }
 
@@ -611,11 +611,11 @@ sexp sexp_make_input_string_port (sexp ctx, sexp str) {
   sexp res;
   sexp_gc_var1(cookie);
   sexp_gc_preserve1(ctx, cookie);
-  cookie = sexp_make_vector(ctx, sexp_make_integer(4), SEXP_VOID);
+  cookie = sexp_make_vector(ctx, sexp_make_fixnum(4), SEXP_VOID);
   sexp_stream_ctx(cookie) = ctx;
   sexp_stream_buf(cookie) = str;
-  sexp_stream_size(cookie) = sexp_make_integer(sexp_string_length(str));
-  sexp_stream_pos(cookie) = sexp_make_integer(0);
+  sexp_stream_size(cookie) = sexp_make_fixnum(sexp_string_length(str));
+  sexp_stream_pos(cookie) = sexp_make_fixnum(0);
   in = funopen(cookie, &sstream_read, NULL, &sstream_seek, NULL);
   res = sexp_make_input_port(ctx, in, SEXP_FALSE);
   sexp_port_cookie(res) = cookie;
@@ -628,12 +628,12 @@ sexp sexp_make_output_string_port (sexp ctx) {
   sexp res, size;
   sexp_gc_var1(cookie);
   sexp_gc_preserve1(ctx, cookie);
-  size = sexp_make_integer(SEXP_INIT_STRING_PORT_SIZE);
-  cookie = sexp_make_vector(ctx, sexp_make_integer(4), SEXP_VOID);
+  size = sexp_make_fixnum(SEXP_INIT_STRING_PORT_SIZE);
+  cookie = sexp_make_vector(ctx, sexp_make_fixnum(4), SEXP_VOID);
   sexp_stream_ctx(cookie) = ctx;
   sexp_stream_buf(cookie) = sexp_make_string(ctx, size, SEXP_VOID);
   sexp_stream_size(cookie) = size;
-  sexp_stream_pos(cookie) = sexp_make_integer(0);
+  sexp_stream_pos(cookie) = sexp_make_fixnum(0);
   out = funopen(cookie, NULL, &sstream_write, &sstream_seek, NULL);
   res = sexp_make_output_port(ctx, out, SEXP_FALSE);
   sexp_port_cookie(res) = cookie;
@@ -646,7 +646,7 @@ sexp sexp_get_output_string (sexp ctx, sexp port) {
   fflush(sexp_port_stream(port));
   return sexp_substring(ctx,
                         sexp_stream_buf(cookie),
-                        sexp_make_integer(0),
+                        sexp_make_fixnum(0),
                         sexp_stream_pos(cookie));
 }
 
@@ -883,8 +883,8 @@ void sexp_write (sexp ctx, sexp obj, sexp out) {
       sexp_write_char(ctx, '>', out);
       break;
     }
-  } else if (sexp_integerp(obj)) {
-    sprintf(numbuf, "%ld", sexp_unbox_integer(obj));
+  } else if (sexp_fixnump(obj)) {
+    sprintf(numbuf, "%ld", sexp_unbox_fixnum(obj));
     sexp_write_string(ctx, numbuf, out);
 #if USE_IMMEDIATE_FLONUMS
   } else if (sexp_flonump(obj)) {
@@ -1024,7 +1024,7 @@ sexp sexp_read_float_tail(sexp ctx, sexp in, sexp_uint_t whole, int negp) {
   if (c=='e' || c=='E') {
     exponent = sexp_read_number(ctx, in, 10);
     if (sexp_exceptionp(exponent)) return exponent;
-    e = (sexp_integerp(exponent) ? sexp_unbox_integer(exponent)
+    e = (sexp_fixnump(exponent) ? sexp_unbox_fixnum(exponent)
          : sexp_flonump(exponent) ? sexp_flonum_value(exponent) : 0.0);
   } else if ((c!=EOF) && ! is_separator(c)) {
     return sexp_read_error(ctx, "invalid numeric syntax",
@@ -1035,7 +1035,7 @@ sexp sexp_read_float_tail(sexp ctx, sexp in, sexp_uint_t whole, int negp) {
   res = ((double)whole + res) * pow(10, e);
   if (negp) res *= -1;
   if ((scale == 0.1) && (exponent != SEXP_VOID) && (res == round(res)))
-    return sexp_make_integer(res);
+    return sexp_make_fixnum(res);
   else
     return sexp_make_flonum(ctx, res);
 }
@@ -1072,11 +1072,11 @@ sexp sexp_read_number(sexp ctx, sexp in, int base) {
     return sexp_read_float_tail(ctx, in, res, negativep);
   } else if (c=='/') {
     den = sexp_read_number(ctx, in, base);
-    if (! sexp_integerp(den))
+    if (! sexp_fixnump(den))
       return (sexp_exceptionp(den)
               ? den : sexp_read_error(ctx, "invalid rational syntax", den, in));
     return sexp_make_flonum(ctx, (double)(negativep ? -res : res)
-                            / (double)sexp_unbox_integer(den));
+                            / (double)sexp_unbox_fixnum(den));
   } else {
     if ((c!=EOF) && ! is_separator(c))
       return sexp_read_error(ctx, "invalid numeric syntax",
@@ -1084,7 +1084,7 @@ sexp sexp_read_number(sexp ctx, sexp in, int base) {
     sexp_push_char(ctx, c, in);
   }
 
-  return sexp_make_integer(negativep ? -res : res);
+  return sexp_make_fixnum(negativep ? -res : res);
 }
 
 sexp sexp_read_raw (sexp ctx, sexp in) {
@@ -1177,7 +1177,7 @@ sexp sexp_read_raw (sexp ctx, sexp in) {
     }
     if ((line >= 0) && sexp_pairp(res)) {
       sexp_pair_source(res)
-        = sexp_cons(ctx, sexp_port_name(in), sexp_make_integer(line));
+        = sexp_cons(ctx, sexp_port_name(in), sexp_make_fixnum(line));
     }
     if (sexp_port_sourcep(in))
       for (tmp=res; sexp_pairp(tmp); tmp=sexp_cdr(tmp))
@@ -1196,12 +1196,12 @@ sexp sexp_read_raw (sexp ctx, sexp in) {
     case 'e':
       res = sexp_read(ctx, in);
       if (sexp_flonump(res))
-        res = sexp_make_integer((sexp_sint_t)sexp_flonum_value(res));
+        res = sexp_make_fixnum((sexp_sint_t)sexp_flonum_value(res));
       break;
     case 'i':
       res = sexp_read(ctx, in);
-      if (sexp_integerp(res))
-        res = sexp_make_flonum(ctx, sexp_unbox_integer(res));
+      if (sexp_fixnump(res))
+        res = sexp_make_flonum(ctx, sexp_unbox_fixnum(res));
       break;
     case 'f':
     case 't':
@@ -1308,7 +1308,7 @@ sexp sexp_read_raw (sexp ctx, sexp in) {
             sexp_bignum_sign(res) = -sexp_bignum_sign(res);
           else
 #endif
-            res = sexp_fx_mul(res, sexp_make_integer(-1));
+            res = sexp_fx_mul(res, sexp_make_fixnum(-1));
       }
     } else {
       sexp_push_char(ctx, c2, in);