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Code Issues 1 Releases Wiki Activity

Add with-syms and combine bignat_add and bignatr mul

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into a single operation for strtod.c
This commit is contained in:
Calvin Rose 2019-01-02 10:23:11 -05:00
parent 0d4ab7dee0
commit 618f8d6818
2 changed files with 11 additions and 29 deletions
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5
src/core/core.janet
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@ -652,6 +652,11 @@
(array/concat res (f x))) (array/concat res (f x)))
res) res)
(defmacro with-syms
"Evaluates body with each symbol in syms bound to a generated, unique symbol."
[syms & body]
~(let ,(mapcat (fn [s] @[s (tuple gensym)]) syms) ,;body))
(defn filter (defn filter
"Given a predicate, take only elements from an array or tuple for "Given a predicate, take only elements from an array or tuple for
which (pred element) is truthy. Returns a new array." which (pred element) is truthy. Returns a new array."

35
src/core/strtod.c
View File

@ -103,33 +103,11 @@ static void bignat_append(struct BigNat *mant, uint32_t dig) {
bignat_extra(mant, 1)[0] = dig; bignat_extra(mant, 1)[0] = dig;
} }
/* Add term to mant */ /* Multiply the mantissa mant by a factor and the add a term
static void bignat_add(struct BigNat *mant, uint32_t dig) { * in one operation. Both factor and term will be between 2 and 36. */
static void bignat_muladd(struct BigNat *mant, uint32_t factor, uint32_t term) {
int32_t i; int32_t i;
int carry = 0; uint64_t carry = ((uint64_t) mant->first_digit) * factor + term;
uint32_t next = mant->first_digit + dig;
if (next >= BIGNAT_BASE) {
next -= BIGNAT_BASE;
carry = 1;
}
mant->first_digit = next;
for (i = 0; i < mant->n; i++) {
if (!carry) return;
uint32_t next = mant->digits[i] + 1;
if (next >= BIGNAT_BASE) {
next = 0;
} else {
carry = 0;
}
mant->digits[i] = next;
}
if (carry) bignat_append(mant, 1);
}
/* Multiply the mantissa mant by a factor */
static void bignat_mul(struct BigNat *mant, uint32_t factor) {
int32_t i;
uint64_t carry = ((uint64_t) mant->first_digit) * factor;
mant->first_digit = carry % BIGNAT_BASE; mant->first_digit = carry % BIGNAT_BASE;
carry /= BIGNAT_BASE; carry /= BIGNAT_BASE;
for (i = 0; i < mant->n; i++) { for (i = 0; i < mant->n; i++) {
@ -238,7 +216,7 @@ static double convert(
/* Positive exponents are simple */ /* Positive exponents are simple */
while (exponent > 0) { while (exponent > 0) {
bignat_mul(mant, base); bignat_muladd(mant, base, 0);
exponent--; exponent--;
} }
@ -331,8 +309,7 @@ double janet_scan_number(
int digit = digit_lookup[*str & 0x7F]; int digit = digit_lookup[*str & 0x7F];
if (*str > 127 || digit >= base) goto error; if (*str > 127 || digit >= base) goto error;
if (seenpoint) ex--; if (seenpoint) ex--;
bignat_mul(&mant, base); bignat_muladd(&mant, base, digit);
bignat_add(&mant, digit);
seenadigit = 1; seenadigit = 1;
} }
str++; str++;