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Float literals were not parsed properly when their fractional part exceeded 53 significant bits. This affected in particular math.PI and math.E. Rather than reinventing the wheel, this patch reuses C's strtod() implementation, which already does the heavy lifting with respect to correctness, though some caution is necessary to keep float parsing locale-independent.
43 lines
1.4 KiB
Nim
43 lines
1.4 KiB
Nim
import math, strutils
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proc c_sprintf(buf, fmt: cstring) {.importc:"sprintf", header: "<stdio.h>", varargs.}
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proc floatToStr(f: float64): string =
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var buffer: array[128, char]
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c_sprintf(buffer, "%.16e", f)
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result = ""
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for ch in buffer:
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if ch == '\0':
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return
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add(result, ch)
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let testFloats = [
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"0", "-1", "1", "1.", ".3", "3.3", "-.3", "-99.99",
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"1.1e10", "-2e100", "1.234e-10", "1.234e+10",
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"-inf", "inf", "+inf",
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"3.14159265358979323846264338327950288",
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"1.57079632679489661923132169163975144",
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"0.785398163397448309615660845819875721",
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"1.41421356237309504880168872420969808",
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"0.707106781186547524400844362104849039",
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"2.71828182845904523536028747135266250",
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"0.00097656250000000021684043449710088680149056017398834228515625"
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]
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for num in testFloats:
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assert num.parseFloat.floatToStr.parseFloat == num.parseFloat
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assert "0".parseFloat == 0.0
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assert "-.1".parseFloat == -0.1
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assert "2.5e1".parseFloat == 25.0
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assert "1e10".parseFloat == 10_000_000_000.0
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assert "0.000_005".parseFloat == 5.000_000e-6
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assert "1.234_567e+2".parseFloat == 123.4567
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assert "1e1_00".parseFloat == "1e100".parseFloat
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assert "3.1415926535897932384626433".parseFloat ==
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3.1415926535897932384626433
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assert "2.71828182845904523536028747".parseFloat ==
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2.71828182845904523536028747
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assert 0.00097656250000000021684043449710088680149056017398834228515625 ==
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"0.00097656250000000021684043449710088680149056017398834228515625".parseFloat
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