[Issue 8882] New: map, filter, iota and zip in pure (and nothrow) functions

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=8882

           Summary: map, filter, iota and zip in pure (and nothrow)
                    functions
           Product: D
           Version: D2
          Platform: x86
        OS/Version: Windows
            Status: NEW
          Keywords: rejects-valid
          Severity: normal
          Priority: P2
         Component: Phobos
        AssignedTo: nobody at puremagic.com
        ReportedBy: bearophile_hugs at eml.cc


--- Comment #0 from bearophile_hugs at eml.cc 2012-10-23 16:43:44 PDT ---
This is not an enhancement request, I think of it as a bug report. This is a
spinoff of Issue 8878

To make functional programming in D a better experience, the following
functions should be usable in a pure (and possibly nothrow) context:


import std.algorithm: map, filter;
import std.range: iota, zip;
void main() pure nothrow {
    auto m = map!q{a * a}([1, 2, 3]);
    auto f = filter!q{ a > 1 }([1, 2, 3]);
    auto i = iota(1, 10, 2);
    auto z = zip([1, 2, 3], [10, 20, 30]);
}


DMD 2.061alpha gives:

test.d(4): Error: pure function 'main' cannot call impure function 'map'
test.d(5): Error: pure function 'main' cannot call impure function 'filter'
test.d(6): Error: pure function 'main' cannot call impure function 'iota'
test.d(7): Error: pure function 'main' cannot call impure function 'zip'
test.d(4): Error: map is not nothrow
test.d(5): Error: filter is not nothrow
test.d(6): Error: iota is not nothrow
test.d(7): Error: zip is not nothrow
test.d(3): Error: function D main 'main' is nothrow yet may throw


Note: zip() accepts a StoppingPolicy, so this can't be nothrow:

import std.range: zip, StoppingPolicy;
void main() pure {
    auto z = zip(StoppingPolicy.requireSameLength, [1,2,3], [10,20]);
    foreach (t; z) {} // throws
}

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------