Bug 251 – foreach does not allow updating inside with block

Array members cannot be updated inside a with block for either structs or classes. Sample code below: import std.stdio; struct Bar { float a= 1.0; } struct Foo { Bar[] arr; } void main( char[][] args ) { Foo foo ;//= new Foo(); foo.arr.length = 20; with(foo) { foreach( int n, Bar bar; arr ) bar.a = 100; } foreach( int n, Bar bar; foo.arr ) writefln("A=%s", bar.a ); }

use inout with(foo) { foreach( int n, inout Bar bar; arr ) bar.a = 100; } haven't tested this but... INVALID I think

BCS wrote: > I think that a basic foreach on an array requiters inout to change things. > > http://www.digitalmars.com/d/statement.html#foreach > > The opApply does requirer the inout (I ran into this a week or so back). This > seems like a problem to me. A non-inout version should be allowed so that > read only access can be granted. I agree too. But I would also like to have a warning or even completely disallow modifications of variables in foreach that are not declared as inout. The present situation is too error-prone: ----------------------------------------------------- foreach(i,k; a) // just forgot to type "inout". code does nothing k=i+1; ----------------------------------------------------- should be ----------------------------------------------------- foreach(i,k; a) k=i+1; // "warning: k is not inout" or "error: k is immutable". foreach(i,inout k; a) // ok k=i+1; ----------------------------------------------------- or maybe just a simple solution is to make them inout by default?

This has nothing to do with it being in a with statement. At one point, the 'key' part of the foreach was set to 'final', meaning it could not be reassigned. This fell afoul of all the tail const problems, so it was abandoned. The current compiler is working as designed. The 'key' value is a mutable copy, unless it is declared as 'inout'.