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Strange results when converting string to float
Moderators:
kris
Posted: 07/09/10 12:57:53Last week I had to process some CSV files (btw. tango.io.stream.Quotes is real cool) and I came across some inconsistencies when converting strings to (float/real) numbers.
To sum it up:
1. I did expect a float (not a real) as result of text.convert.Float.parse
2. text.convert.Float happily converts several things that IMHO aren't numbers
3. util.Convert fails on "0E0"
4. why is it that "-0" becomes -0 but "-0x0" becomes 0?
I made a little test program (using Tangobos for phobos std.conv)
module conv; import tango.io.Stdout; import Float = tango.text.convert.Float; import Convert = tango.util.Convert; import Phobos = std.conv; int main (char[][] args) { // types Stdout.formatln("Types:\n convert.Float -> {}\n util.Convert -> {}\n", typeof(Float.parse("1")).stringof, typeof(Convert.to!(float)("1")).stringof ); // results char[][] strings = [ "", "-", ".", "-.", "*", "E", "-E", "0E0", "-0E0", "0E1", "1E0", "2E0", "2E0.5", "0x", "x0", "-x0", "0", "-0", "0x0", "-0x0", "0x1", "-0x1", ]; Stdout.formatln("Results:"); foreach(i, s; strings) { auto f = Float.parse(s); auto g = Convert.to!(float)(s, float.nan); float p; try { p = Phobos.toFloat(s); } catch(Object o) { p = float.nan; } Stdout.formatln("{:d3}: '{}'", 1+i, s); Stdout.formatln(" convert.Float: {}", Float.toString(f)); Stdout.formatln(" util.Convert: {}", Float.toString(g)); Stdout.formatln(" std.conv: {}\n", Float.toString(p)); } return 0; }and it gave me these results:
Types: convert.Float -> real util.Convert -> float Results: 001: '' convert.Float: nan util.Convert: nan std.conv: nan 002: '-' convert.Float: nan util.Convert: nan std.conv: nan 003: '.' convert.Float: 0 util.Convert: 0 std.conv: nan 004: '-.' convert.Float: -0 util.Convert: -0 std.conv: nan 005: '*' convert.Float: 0 util.Convert: nan std.conv: nan 006: 'E' convert.Float: 0 util.Convert: nan std.conv: nan 007: '-E' convert.Float: -0 util.Convert: nan std.conv: nan 008: '0E0' convert.Float: 0 util.Convert: nan std.conv: 0 009: '-0E0' convert.Float: -0 util.Convert: nan std.conv: -0 010: '0E1' convert.Float: 0 util.Convert: nan std.conv: 0 011: '1E0' convert.Float: 1 util.Convert: 1 std.conv: 1 012: '2E0' convert.Float: 2 util.Convert: 2 std.conv: 2 013: '2E0.5' convert.Float: 2 util.Convert: nan std.conv: nan 014: '0x' convert.Float: nan util.Convert: nan std.conv: nan 015: 'x0' convert.Float: 0 util.Convert: nan std.conv: nan 016: '-x0' convert.Float: -0 util.Convert: nan std.conv: nan 017: '0' convert.Float: 0 util.Convert: 0 std.conv: 0 018: '-0' convert.Float: -0 util.Convert: -0 std.conv: -0 019: '0x0' convert.Float: 0 util.Convert: 0 std.conv: nan 020: '-0x0' convert.Float: 0 util.Convert: 0 std.conv: nan 021: '0x1' convert.Float: 1 util.Convert: 1 std.conv: nan 022: '-0x1' convert.Float: -1 util.Convert: -1 std.conv: nan
