[Issue 10309] New: rightSplit() and second argoment for split()

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=10309

           Summary: rightSplit() and second argoment for split()
           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 2013-06-08 15:19:30 PDT ---
If I have a string as "10,20,30" and I need to split it taking the part after
the last comma and all before it, in Python I use rsplit() with optional
argument 1:


>>> s = "10,20,30"
>>> a, b = s.rsplit(",", 1)
>>> assert a, b == "10,20", "30"


The optional second argument tells Python when to stop splitting, and the "r"
suffix of split means "from the right":

>>> "10,20,30,40,50".rsplit(",", 2)
['10,20,30', '40', '50']
>>> "10,20,30,40,50".split(",", 2)
['10', '20', '30,40,50']


One (awkward) way to do the same thing in D+Phobos is:

import std.algorithm: find;
import std.range: retro;
void main() {
    auto s = "10,20,30";
    string a = s.retro.find(",").retro[0 .. $ - 1];
    string b = s[a.length + 1 .. $];
    assert (a == "10,20");
    assert(b == "30");
}



I don't see a rsplit or rSplit or rightSplit in std.string, but I see
findSplitAfter and findSplitBefore in std.algorithm:

s.findSplitAfter(",")
==>
Tuple!(string, string)("10,", "20,30")

s.findSplitBefore(",")
==>
Tuple!(string, string)("10", ",20,30")


If I use std.range.retro:
s.retro.findSplitBefore(",")
==>
Tuple!(Result, Result)(03, ,02,01)

Also notice the lack of " inside the tuple, those aren't strings.

And indeed this is not accepted:
s.retro.findSplitBefore(",")[0].retro


If I am not missing something from Phobos, then maybe it's a good idea to add a
rSplit(string,count=-1) (or rightSplit) to std.string or std.array (and maybe
add a second argument to std.array.split as in Python).

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