Decimal string parsing isn't IEEE compatible

[dlangBugzillaToGithub]

ilyayaroshenko reported this on 2020-06-21T13:57:02Z

Transfered from https://issues.dlang.org/show_bug.cgi?id=20967

CC List

• bugzilla (@WalterBright)

Description

import std.conv;
void main() {
    assert("1.448997445238699".to!double == 0x1.72f17f1f49aadp0);
}

[dlangBugzillaToGithub]

bugzilla (@WalterBright) commented on 2021-03-25T06:32:23Z

Verified this. Left side produces 0x1.72f17f1f49aaep0 but right side is the correct value.

[Aditya-132]

Working on it

[cyrusmsk]

Catch by mojo:

{
    ulong msdec = 1448997445238699;       
    printf("%a\n", cast(double)(msdec / 1e15)); // 0x1.72f17f1f49aadp+0
}

but

{
    printf("%a\n", cast(double)(1448997445238699UL / 1e15)); // 0x1.72f17f1f49aaep+0
}