8000 py: Implement raising a big-int to a negative power. · lable/micropython@04552ff · GitHub
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py: Implement raising a big-int to a negative power.
Before this patch raising a big-int to a negative power would just return 0. Now it returns a floating-point number with the correct value.
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5 files changed

+19
-4
lines changed

5 files changed

+19
-4
lines changed

‎py/mpz.c

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Original file line numberDiff line numberDiff line change
@@ -946,10 +946,6 @@ bool mpz_is_pos(const mpz_t *z) {
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return z->len > 0 && z->neg == 0;
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}
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bool mpz_is_neg(const mpz_t *z) {
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return z->len > 0 && z->neg != 0;
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}
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bool mpz_is_odd(const mpz_t *z) {
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return z->len > 0 && (z->dig[0] & 1) != 0;
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}

‎py/mpz.h

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Original file line numberDiff line numberDiff line change
@@ -112,6 +112,7 @@ size_t mpz_set_from_str(mpz_t *z, const char *str, size_t len, bool neg, unsigne
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void mpz_set_from_bytes(mpz_t *z, bool big_endian, size_t len, const byte *buf);
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static inline bool mpz_is_zero(const mpz_t *z) { return z->len == 0; }
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static inline bool mpz_is_neg(const mpz_t *z) { return z->len != 0 && z->neg != 0; }
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int mpz_cmp(const mpz_t *lhs, const mpz_t *rhs);
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void mpz_abs_inpl(mpz_t *dest, const mpz_t *z);

‎py/objint_longlong.c

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -191,6 +191,13 @@ mp_obj_t mp_obj_int_binary_op(mp_uint_t op, mp_obj_t lhs_in, mp_obj_t rhs_in) {
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case MP_BINARY_OP_POWER:
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case MP_BINARY_OP_INPLACE_POWER: {
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if (rhs_val < 0) {
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#if MICROPY_PY_BUILTINS_FLOAT
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return mp_obj_float_binary_op(op, lhs_val, rhs_in);
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#else
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mp_raise_ValueError("negative power with no float support");
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#endif
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}
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long long ans = 1;
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while (rhs_val > 0) {
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if (rhs_val & 1) {

‎py/objint_mpz.c

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -290,6 +290,13 @@ D76A mp_obj_t mp_obj_int_binary_op(mp_uint_t op, mp_obj_t lhs_in, mp_obj_t rhs_in) {
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case MP_BINARY_OP_POWER:
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case MP_BINARY_OP_INPLACE_POWER:
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if (mpz_is_neg(zrhs)) {
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#if MICROPY_PY_BUILTINS_FLOAT
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return mp_obj_float_binary_op(op, mpz_as_float(zlhs), rhs_in);
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#else
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mp_raise_ValueError("negative power with no float support");
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#endif
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}
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mpz_pow_inpl(&res->mpz, zlhs, zrhs);
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break;
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‎tests/float/int_big_float.py

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Original file line numberDiff line numberDiff line change
@@ -18,6 +18,10 @@
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# this should delegate to complex
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print("%.5g" % (i * 1.2j).imag)
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# negative power should produce float
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print("%.5g" % (i ** -1))
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print("%.5g" % ((2 + i - i) ** -3))
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try:
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i / 0
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except ZeroDivisionError:

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