[Issue 11084] New: std.algorithm.scan

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=11084

           Summary: std.algorithm.scan
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: Phobos
        AssignedTo: nobody at puremagic.com
        ReportedBy: bearophile_hugs at eml.cc


--- Comment #0 from bearophile_hugs at eml.cc 2013-09-21 05:47:16 PDT ---
I suggest to add to Phobos a function that returns a range, with usage very
similar to std.algorithm.reduce, that returns all the intermediate values.

An example from Haskell:

Prelude> [1 .. 10]
[1,2,3,4,5,6,7,8,9,10]
Prelude> scanl (+) 0 [1 .. 10]
[0,1,3,6,10,15,21,28,36,45,55]
Prelude> scanr (+) 0 [1 .. 10]
[55,54,52,49,45,40,34,27,19,10,0]


That is also related to the FoldList of Mathematica:
http://reference.wolfram.com/mathematica/ref/FoldList.html


In D it could work like this:

iota(1, 11).scan!q{a + b}(0).writeln
==> 
[0, 1, 3, 6, 10, 15, 21, 28, 36, 45, 55]

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