8000 [Backport 3.3] [Bug #20654] Fix floor and ceil when ndigits is large by peterzhu2118 · Pull Request #11277 · ruby/ruby · GitHub
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[Backport 3.3] [Bug #20654] Fix floor and ceil when ndigits is large #11277

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Merged
merged 2 commits into from
Jul 30, 2024
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[Backport 3.3] [Bug #20654] Fix floor and ceil when ndigits is large #11277

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94d3bd9
Fix floor when ndigits is large
peterzhu2118 Jul 26, 2024
1a46429
Fix ceil when ndigits is large
peterzhu2118 Jul 26, 2024
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Fix floor when ndigits is large 
[Bug #20654]

This commit fixes Integer#floor and Float#floor when the number is
negative and ndigits is large such that 10**ndigits is a bignum.

Previously, it would return 0 in such cases. However, this would cause
unexpected behaviour such as:

    puts -1.floor(-5) # => -100000
    puts -1.floor(-10) # => -10000000000
    puts -1.floor(-20) # => 0

This commit changes the last result so that it will return
-100000000000000000000.
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@peterzhu2118
peterzhu2118 committed Jul 29, 2024
commit 94d3bd962f802f9eb78aa346eafce6a843ff8b96
16 changes: 7 additions & 9 deletions numeric.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2373,11 +2373,7 @@ rb_int_round(VALUE num, int ndigits, enum ruby_num_rounding_mode mode)
static VALUE
rb_int_floor(VALUE num, int ndigits)
{
VALUE f;

if (int_round_zero_p(num, ndigits))
return INT2FIX(0);
f = int_pow(10, -ndigits);
VALUE f = int_pow(10, -ndigits);
if (FIXNUM_P(num) && FIXNUM_P(f)) {
SIGNED_VALUE x = FIX2LONG(num), y = FIX2LONG(f);
int neg = x < 0;
Expand All @@ -2386,11 +2382,13 @@ rb_int_floor(VALUE num, int ndigits)
if (neg) x = -x;
return LONG2NUM(x);
}
if (RB_FLOAT_TYPE_P(f)) {
/* then int_pow overflow */
return INT2FIX(0);
else {
bool neg = int_neg_p(num);
if (neg) num = rb_int_minus(rb_int_plus(rb_int_uminus(num), f), INT2FIX( 8000 1));
num = rb_int_mul(rb_int_div(num, f), f);
if (neg) num = rb_int_uminus(num);
return num;
}
return rb_int_minus(num, rb_int_modulo(num, f));
}

static VALUE
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4 changes: 4 additions & 0 deletions test/ruby/test_float.rb
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Expand Up @@ -530,6 +530,10 @@ def test_floor_with_precision
assert_raise(TypeError) {1.0.floor(nil)}
def (prec = Object.new).to_int; 2; end
assert_equal(0.99, 0.998.floor(prec))

assert_equal(-10000000000, -1.0.floor(-10), "[Bug #20654]")
assert_equal(-100000000000000000000, -1.0.floor(-20), "[Bug #20654]")
assert_equal(-100000000000000000000000000000000000000000000000000, -1.0.floor(-50), "[Bug #20654]")
end

def test_ceil_with_precision
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4 changes: 4 additions & 0 deletions test/ruby/test_integer.rb
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Expand Up @@ -465,6 +465,10 @@ def test_floor

assert_int_equal(1111_1111_1111_1111_1111_1111_1111_1111, 1111_1111_1111_1111_1111_1111_1111_1111.floor(1))
assert_int_equal(10**400, (10**400).floor(1))

assert_int_equal(-10000000000, -1.floor(-10), "[Bug #20654]")
assert_int_equal(-100000000000000000000, -1.floor(-20), "[Bug #20654]")
assert_int_equal(-100000000000000000000000000000000000000000000000000, -1.floor(-50), "[Bug #20654]")
end

def test_ceil
Expand Down
0