http://d.puremagic.com/issues/show_bug.cgi?id=6383
Summary: Unpacking from dynamic array, lazy ranges Product: D Version: D2 Platform: All OS/Version: All Status: NEW Severity: enhancement Priority: P2 Component: DMD AssignedTo: nob...@puremagic.com ReportedBy: bearophile_h...@eml.cc --- Comment #0 from bearophile_h...@eml.cc 2011-07-26 06:52:19 PDT --- This is a spinoff of Issue 6365 (AutoTupleDeclaration). Issue 6365 is about syntax sugar to unpack tuples, but unpacking dynamic arrays or lazy ranges too is handy and commonly useful, because in D most arrays are not fixed-sized, and many functions return a lazy range, like lazy splitting, regular expression matches, etc. The 'lengths don't match' exception is already present in D and I think it's acceptable (when the lengths are statically known there is no need to test lengths at run time, so this exception throwing is not present, so it's nothrow code): int[] array = [1, 2, 3]; int[2] a2 = array[]; ------------------- Some usage examples, assign from a dynamic array, in D2: import std.string; void main() { auto s = " foo bar "; auto ss = s.split(); auto sa = ss[0]; auto sb = ss[1]; } In Python2.6: >>> sa, sb = " foo bar ".split() >>> sa 'foo' >>> sb 'bar' Proposed: import std.string; void main() { auto s = " foo bar "; auto (sa, sb) = s.split(); } ------------------- >From lazy range, D2: import std.algorithm, std.conv, std.string; void main() { string s = " 15 27"; // splitter doesn't work yet for this // (here it doesn't strip the leading space) //auto xy = map!(to!int)(splitter(s)); auto xy = map!(to!int)(split(s)); int x = xy[0]; int y = xy[1]; } In Python: >>> x, y = map(int, " 15 27".split()) >>> x 15 >>> y 27 >>> from itertools import imap >>> x, y = imap(int, " 15 27".split()) >>> x 15 >>> y 27 Proposed: import std.algorithm, std.conv, std.string; void main() { string s = " 15 27"; (int x, int y) = map!(to!int)(splitter(s)); } ------------------- >From a lazy range, another example. See: http://rosettacode.org/wiki/Range_expansion#D D2 code: import std.stdio, std.regex, std.string, std.conv, std.range; int[] rangeExpand(string txt) { int[] result; foreach (r; std.string.split(txt, ",")) { auto m = array(match(r, r"^(-?\d+)(-?(-?\d+))?$").captures); if (m[2].empty) result ~= to!int(m[1]); else result ~= array(iota(to!int(m[1]), to!int(m[3])+1)); } return result; } Python: import re def rangeexpand(txt): lst = [] for rng in txt.split(','): start,end = re.match('^(-?\d+)(?:-(-?\d+))?$', rng).groups() if end: lst.extend(xrange(int(start),int(end)+1)) else: lst.append(int(start)) return lst print(rangeexpand('-6,-3--1,3-5,7-11,14,15,17-20')) Proposed (just the important line), from dynamic array: auto (start,end) = array(match(r, r"^(-?\d+)(-?(-?\d+))?$").captures); Or better, from the range of regex captures: auto (start,end) = match(r, r"^(-?\d+)(-?(-?\d+))?$").captures; Similar unpacking from Python list (that is a dynamic array) or from lazy iterable is quite common in scripting-style Python code. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------