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Fix (expt bignum -k)

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Bertrand Augereau 2018-06-10 03:00:38 +02:00
parent 4d8933119f
commit d88dfeb172
1 changed files with 10 additions and 3 deletions
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13
bignum.c
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@ -610,14 +610,21 @@ 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_fx_abs(b);
sexp_sint_t e = sexp_unbox_fixnum(b);
sexp_sint_t abs_e;
if (e < 0)
abs_e = -e;
else
abs_e = e;
sexp_gc_var2(res, acc);
sexp_gc_preserve2(ctx, res, acc);
res = sexp_fixnum_to_bignum(ctx, SEXP_ONE);
acc = sexp_copy_bignum(ctx, NULL, a, 0);
for (; e; e>>=1, acc=sexp_bignum_mul(ctx, NULL, acc, acc))
if (e & 1)
for (; abs_e; abs_e>>=1, acc=sexp_bignum_mul(ctx, NULL, acc, acc))
if (abs_e & 1)
res = sexp_bignum_mul(ctx, NULL, res, acc);
if (e < 0)
res = sexp_div(ctx, sexp_fixnum_to_bignum(ctx, SEXP_ONE), res);
sexp_gc_release2(ctx);
return sexp_bignum_normalize(res);
}