From 92896d22026ad8b95622a9c21d57df8d9f7e3269 Mon Sep 17 00:00:00 2001
From: Justin Ethier <justin.ethier@gmail.com>
Date: Wed, 19 May 2021 18:50:45 -0700
Subject: [PATCH] Issue #459 - R7RS #d decimal specifier

---
 CHANGELOG.md |  1 +
 runtime.c    | 26 ++++++++++++++++++--------
 2 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3978b9d3..9972cf29 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,7 @@
 Features
 
 - Improve performance of runtime by more efficiently unboxing known fixnums. 
+- Add support for R7RS `#d` decimal specifier for numbers.
 
 Bug Fixes
 
diff --git a/runtime.c b/runtime.c
index 38f511ce..17f2d513 100644
--- a/runtime.c
+++ b/runtime.c
@@ -7553,14 +7553,22 @@ static void _read_return_number(void *data, port_type *p, int base, int exact)
   // TODO: validation?
   p->tok_buf[p->tok_end] = '\0'; // TODO: what if buffer is full?
   p->tok_end = 0; // Reset for next atom
-  make_empty_vector(vec);
-  make_string(str, p->tok_buf);
-  vec.num_elements = 3;
-  vec.elements = (object *) alloca(sizeof(object) * vec.num_elements);
-  vec.elements[0] = &str;
-  vec.elements[1] = obj_int2obj(base);
-  vec.elements[2] = exact ? boolean_t : boolean_f;
-  return_thread_runnable_with_obj(data, &vec, p);
+  if (exact > 1) {
+    // Special case, we don't know if exact or inexact
+    make_string(str, p->tok_buf);
+    str.num_cp = Cyc_utf8_count_code_points((uint8_t *)(p->tok_buf));
+    make_c_opaque(opq, &str);
+    return_thread_runnable_with_obj(data, &opq, p);
+  } else {
+    make_empty_vector(vec);
+    make_string(str, p->tok_buf);
+    vec.num_elements = 3;
+    vec.elements = (object *) alloca(sizeof(object) * vec.num_elements);
+    vec.elements[0] = &str;
+    vec.elements[1] = obj_int2obj(base);
+    vec.elements[2] = exact ? boolean_t : boolean_f;
+    return_thread_runnable_with_obj(data, &vec, p);
+  }
 }
 
 /**
@@ -7962,6 +7970,8 @@ void Cyc_io_read_token(void *data, object cont, object port)
         return_thread_runnable_with_obj(data, boolean_f, p);
       } else if (c == '\\') {
         _read_character(data, p);
+      } else if (c == 'd') {
+        _read_number(data, p, 10, 2);
       } else if (c == 'e') {
         _read_number(data, p, 10, 1);
       } else if (c == 'i') {