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Merged
kou merged 2 commits into from
Dec 1, 2025
Merged

Add expt #26

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d573227
Add expt
jpellegrini Nov 30, 2025
dafdf99
Update test/test-number-arith.scm
jpellegrini Dec 1, 2025
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1 change: 0 additions & 1 deletion doc/spec.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -439,7 +439,6 @@ Numbers
- *procedure:* atan z
- *procedure:* atan y x
- *procedure:* sqrt z
- *procedure:* expt z1 z2
- *procedure:* make-rectangular x1 x2
- *procedure:* make-polar x3 x4
- *procedure:* real-part z
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28 changes: 28 additions & 0 deletions src/number.c
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Expand Up @@ -45,6 +45,7 @@
=======================================*/
#define ERRMSG_DIV_BY_ZERO "division by zero"
#define ERRMSG_REQ_1_ARG "at least 1 argument required"
#define ERRMSG_NEGATIVE_EXP "negative exponent"

/*=======================================
File Local Type Definitions
Expand Down Expand Up @@ -417,3 +418,30 @@ scm_p_remainder(ScmObj _n1, ScmObj _n2)

return MAKE_INT(n1 % n2);
}

SCM_EXPORT ScmObj
scm_p_expt(ScmObj _base, ScmObj _expo)
{
scm_int_t base, expo, result;
DECLARE_FUNCTION("expt", procedure_fixed_2);

ENSURE_INT(_base);
ENSURE_INT(_expo);

base = SCM_INT_VALUE(_base);
expo = SCM_INT_VALUE(_expo);

/* SigScheme only implements integer numbers, so negative
exponents are not allowed. */
if (expo < 0) ERR(ERRMSG_NEGATIVE_EXP);
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@kou kou Nov 30, 2025 •
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Could you add a comment why we return an error here?

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@jpellegrini jpellegrini Dec 1, 2025

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Ok, done!


result = 1;
while (expo > 0) {
if (expo % 2 == 1)
result *= base;
base *= base;
expo /= 2;
}

return MAKE_INT(result);
}
1 change: 1 addition & 0 deletions src/sigscheme.h
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Expand Up @@ -1474,6 +1474,7 @@ SCM_EXPORT ScmObj scm_p_abs(ScmObj _n);
SCM_EXPORT ScmObj scm_p_quotient(ScmObj _n1, ScmObj _n2);
SCM_EXPORT ScmObj scm_p_modulo(ScmObj _n1, ScmObj _n2);
SCM_EXPORT ScmObj scm_p_remainder(ScmObj _n1, ScmObj _n2);
SCM_EXPORT ScmObj scm_p_expt(ScmObj _n1, ScmObj _n2);
#endif /* SCM_USE_NUMBER */

/* number-io.c */
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8 changes: 8 additions & 0 deletions test/test-number-arith.scm
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Expand Up @@ -1843,5 +1843,13 @@
-9223372036854775808))"))
(else
(assert-fail (tn) "unknown int bitwidth")))
(tn "expt")
(assert-equal? (tn) 9 (expt 3 2))
(assert-equal? (tn) 9 (expt -3 2))
(assert-equal? (tn) 27 (expt 3 3))
(assert-equal? (tn) -27 (expt -3 3))
(assert-equal? (tn) 1 (expt -3 0))
(assert-equal? (tn) 0 (expt 0 11))
(assert-error (tn) (lambda () (expt 3 -2)))

(total-report)