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std.fmt.parse_float: Fix exponent calculation

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This was incorrectly translated as a u64. binary_exponent is an
unadjusted value so can be negative. In becomes unconditionally positive
when adding the bias.
This commit is contained in:
Marc Tiehuis 2019-05-20 17:28:17 +12:00
parent 1c73c08298
commit 163a8e98bc
1 changed files with 3 additions and 2 deletions
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5
std/fmt/parse_float.zig
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@ -103,7 +103,7 @@ fn convertRepr(comptime T: type, n: FloatRepr) T {
s.d1 = @truncate(u32, n.mantissa >> 32);
s.d2 = 0;
var binary_exponent: u64 = 92;
var binary_exponent: i32 = 92;
var exp = n.exponent;
while (exp > 0) : (exp -= 1) {
@ -161,7 +161,7 @@ fn convertRepr(comptime T: type, n: FloatRepr) T {
} else if (binary_exponent < 1) {
break :blk if (n.negative) f64_minus_zero else f64_plus_zero;
} else if (s.d2 != 0) {
const binexs2 = u64(binary_exponent) << 52;
const binexs2 = @intCast(u64, binary_exponent) << 52;
const rr = (u64(s.d2 & ~mask28) << 24) | ((u64(s.d1) + 128) >> 8) | binexs2;
break :blk if (n.negative) rr | (1 << 63) else rr;
} else {
@ -415,6 +415,7 @@ test "fmt.parseFloat" {
if (T != f16) {
expect(approxEq(T, try parseFloat(T, "123142.1"), 123142.1, epsilon));
expect(approxEq(T, try parseFloat(T, "-123142.1124"), T(-123142.1124), epsilon));
expect(approxEq(T, try parseFloat(T, "0.7062146892655368"), T(0.7062146892655368), epsilon));
}
}
}