From 4a2e736594f07cbfed8e35eda5ee5ac9157c7f47 Mon Sep 17 00:00:00 2001 From: "K. Lange" Date: Wed, 28 Feb 2024 07:16:18 +0900 Subject: [PATCH] Use 10^52, as that makes more sense. --- src/obj_long.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/src/obj_long.c b/src/obj_long.c index 99ce2b4..d10e664 100644 --- a/src/obj_long.c +++ b/src/obj_long.c @@ -2414,14 +2414,14 @@ KrkValue krk_double_to_string(double a, int exact, unsigned int digits, char for } if (e == -1023 && m == 0) return OBJECT_VAL(S("0.0")); - /* We need to cache the decimal versions of each necessary division of 10⁵⁵, if we've not seen them before. */ + /* We need to cache the decimal versions of each necessary division of 10⁵², if we've not seen them before. */ KrkValue float_decimal_parts = NONE_VAL(); if (!krk_tableGet_fast(&vm.baseClasses->floatClass->methods, S("__decimals__"), &float_decimal_parts)) { krk_push(OBJECT_VAL(krk_newTuple(54))); float_decimal_parts = krk_peek(0); KrkLong d; - krk_long_parse_string("10000000000000000000000000000000000000000000000000000000", &d, 10, 56); + krk_long_parse_string("10000000000000000000000000000000000000000000000000000", &d, 10, 53); for (int i = 0; i < 53; ++i) { AS_TUPLE(float_decimal_parts)->values.values[AS_TUPLE(float_decimal_parts)->values.count++] = make_long_obj(&d); @@ -2433,6 +2433,8 @@ KrkValue krk_double_to_string(double a, int exact, unsigned int digits, char for } } + /* We use 10^31 to add additional digits to ensure right shifting does not result + * in dropped bits when converting the base-2 exponent to base-10. */ KrkLong f; krk_long_parse_string("10000000000000000000000000000000", &f, 10, 32); AS_TUPLE(float_decimal_parts)->values.values[AS_TUPLE(float_decimal_parts)->values.count++] = make_long_obj(&f); @@ -2444,7 +2446,7 @@ KrkValue krk_double_to_string(double a, int exact, unsigned int digits, char for /* Given that a double takes the form 2ⁿ × m, where either 1.0 ≤ m < 2.0 or * (for subnormals) 0 < m < 1.0, generate a decimal representation of m as the - * numerator in a fraction with 10⁵⁵ as the denominator. For example, the + * numerator in a fraction with 10⁵² as the denominator. For example, the * value 123.456 is represented as: * 2⁶ × 1.9290000000000000479616346638067625463008880615234375 * So we want to have the value: @@ -2461,7 +2463,7 @@ KrkValue krk_double_to_string(double a, int exact, unsigned int digits, char for e = -1022; } else { /* Otherwise, our decimal representation of the multiplier will start with a 1, so - * start us off with 10⁵⁵ from above. */ + * start us off with 10⁵² from above. */ krk_long_init_copy(&c, AS_long(AS_TUPLE(float_decimal_parts)->values.values[0])->value); } @@ -2472,12 +2474,12 @@ KrkValue krk_double_to_string(double a, int exact, unsigned int digits, char for } } - /* At this point, we know that we have 55 decimal digits to the right of the radix point; + /* At this point, we know that we have 52 decimal digits to the right of the radix point; * this represents the base-10 exponent of our denominator. We want to maintain an exact * value for m after turning the base-2 exponent into a base-10 exponent, so if our * original base-2 exponent is negative, we might need to add more 0s to the end of * both the top and bottom of the fraction - we'll add to b to account for that. */ - int b = 55; + int b = 52; if (e < 0) { /* Repeatedly multiply to increase number of decimal digits by 31, until the resulting