## digitalmars.D.bugs - [Issue 5530] New: std.algorithm.len()

```http://d.puremagic.com/issues/show_bug.cgi?id=5530

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

--- Comment #0 from bearophile_hugs eml.cc 2011-02-05 17:22:30 PST ---
A simple task asks to sort an array according to the length of its items. This
is a D2 solution:

import std.stdio, std.algorithm;
void main() {
auto l =
[['a','b','c'],['d','e'],['f','g','h'],['i','j','k','l'],['m','n'],['o']];
schwartzSort!((s){return s.length; })(l);
writeln(l);
}

It's supposed to print:
[['o'], ['d', 'e'], ['m', 'n'], ['a', 'b', 'c'], ['f', 'g', 'h'], ['i', 'j',
'k', 'l']]

I suggest to add a simple len() function to std.algorithm, that allows to
shorten that very common code (mapping lengths is a very common operation):

import std.stdio, std.algorithm;
size_t len(Range)(Range r) if (is(typeof(r.length))) {
return r.length;
}
void main() {
auto l =
[['a','b','c'],['d','e'],['f','g','h'],['i','j','k','l'],['m','n'],['o']];
schwartzSort!len(l);
writeln(l);
}

In Python the "len()" function is a free function to allow it to be used as
mapping function, sorting function for a Schwartz sort, etc. In Ruby there is a
"size" standard attribute, and blocks are more used.

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Feb 05 2011