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digitalmars.D.bugs - [Issue 4111] New: Foreach ranges accept floating-point extrema

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=4111

           Summary: Foreach ranges accept floating-point extrema
           Product: D
           Version: future
          Platform: All
        OS/Version: All
            Status: NEW
          Keywords: accepts-invalid
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: bearophile_hugs eml.cc


--- Comment #0 from bearophile_hugs eml.cc 2010-04-21 14:01:40 PDT ---
This D2 code works with dmd 2.043, it shows that foreach accepts floating point
extrema too.

But I think it's safer/tidier to accept only ranges with integral extrema (in
Python too the range/xrange expects integers). FP approximations can cause
problems here.


import std.stdio;
import std.math: nextUp;
void main() {
    foreach(i; 2.1 .. 4.10001) {
        writeln(typeid(typeof(i))); // Output: double
        break;
    }
    foreach(i; 2.1 .. nextUp(4.1))
        write(i, " "); // Output: 2.1 3.1 4.1
}

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Apr 21 2010
next sibling parent reply "Aelxx" <aelxx yandex.ru> writes:
    foreach(i; 2.1 .. 4.10001) {
        writeln(typeid(typeof(i))); // Output: double
        break;
    }
I'd like MATLAB style more: foreach (f; linspace (0.0, 1.0, 100)) {...} here f gets values 0, 0.0101.., 0.0202..., ..., 0.98989..., 1.0 foreach (f; logspace (1.0, 1e6, 7)) {...} here f gets values 1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6.
Apr 21 2010
parent bearophile <bearophileHUGS lycos.com> writes:
Aelxx:
    foreach(i; 2.1 .. 4.10001) {
        writeln(typeid(typeof(i))); // Output: double
        break;
    }
I'd like MATLAB style more: foreach (f; linspace (0.0, 1.0, 100)) {...} here f gets values 0, 0.0101.., 0.0202..., ..., 0.98989..., 1.0 foreach (f; logspace (1.0, 1e6, 7)) {...} here f gets values 1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6.
If you have comments on a bug report, it's quite better if you write them in Bugzilla, because here they will probably be lost/ignored. Phobos has iota() that's similar to what you ask, a FP version is easy to create. Bye, bearophile
Apr 22 2010
prev sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=4111



--- Comment #1 from bearophile_hugs eml.cc 2010-04-22 02:09:06 PDT ---
Aelxx (aelxx at yandex dot ru) suggests:

I'd like MATLAB style more:
foreach (f; linspace (0.0, 1.0, 100))
{...}
here f gets values 0, 0.0101.., 0.0202..., ..., 0.98989..., 1.0

foreach (f; logspace (1.0, 1e6, 7))
{...}
here f gets values 1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6.

------------------------

My answer:

Phobos has iota() that's similar to what you ask, a FP version is easy to
create. With iota even the current interval syntax becomes less useful.
See also bug 4112.

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Apr 22 2010