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April 22, 2012 What am I doing wrong ? | ||||
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Sorry for the noob questions, but import std.stdio; struct Foo { int x; } void main() { auto array = new Foo[10]; auto i = array.length; foreach(Foo f; array) { f.x = --i; write(f.x);} writeln(); foreach(Foo f; array) { write(f.x);} } gives me: PS E:\DigitalMars\dmd2\samples> rdmd bug.d 9876543210 0000000000 Also, void main() { auto array = new Foo[10]; --> for(int i = array.length; i > 1; i--) { array[i].x = i; } writeln(); foreach(Foo f; array) { write(f.x);} } throws core.exception.RangeError@bug(8): Range violation on the line with the arrow. What am I doing wrong ? |
April 22, 2012 Re: What am I doing wrong ? | ||||
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Posted in reply to SomeDude | On 23.04.2012 1:47, SomeDude wrote: > Sorry for the noob questions, but > > import std.stdio; > > struct Foo { > int x; > } > void main() { > auto array = new Foo[10]; > auto i = array.length; > foreach(Foo f; array) { f.x = --i; write(f.x);} > writeln(); > foreach(Foo f; array) { write(f.x);} Here: Foo f is not a reference but a copy of each array element. Use foreach( ref f; array) > } > > gives me: > > PS E:\DigitalMars\dmd2\samples> rdmd bug.d > 9876543210 > 0000000000 > > Also, > > void main() { > auto array = new Foo[10]; > --> for(int i = array.length; i > 1; i--) { array[i].x = i; } Arrays indices are 0 based, thus last index is array.length-1. > writeln(); > foreach(Foo f; array) { write(f.x);} > } > > throws core.exception.RangeError@bug(8): Range violation on the line > with the arrow. > > What am I doing wrong ? -- Dmitry Olshansky |
April 22, 2012 Re: What am I doing wrong ? | ||||
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Posted in reply to SomeDude | On 04/22/2012 11:47 PM, SomeDude wrote: > Sorry for the noob questions, but > > import std.stdio; > > struct Foo { > int x; > } > void main() { > auto array = new Foo[10]; > auto i = array.length; > foreach(Foo f; array) { f.x = --i; write(f.x);} Use ref when you want to modify the original array, without ref you are modifying a copy in the foreach. foreach(ref Foo f; array) { f.x = --i; write(f.x);} > writeln(); > foreach(Foo f; array) { write(f.x);} > } > > gives me: > > PS E:\DigitalMars\dmd2\samples> rdmd bug.d > 9876543210 > 0000000000 > > Also, > > void main() { > auto array = new Foo[10]; > --> for(int i = array.length; i > 1; i--) { array[i].x = i; } > writeln(); > foreach(Foo f; array) { write(f.x);} > } > > throws core.exception.RangeError@bug(8): Range violation on the line > with the arrow. > > What am I doing wrong ? You set i to the array length of 10 but the array index is zero based so the last item in the array is at index 9. But in the first iteration of the loop you are trying to access the the item at index 10 (array.length) which doesn't exist. -- Mike Wey |
April 22, 2012 Re: What am I doing wrong ? | ||||
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Posted in reply to Dmitry Olshansky | On Sunday, 22 April 2012 at 21:50:32 UTC, Dmitry Olshansky wrote: Omagad, thank you, too much Java is baaaad for your brains. |
April 26, 2012 Re: What am I doing wrong ? | ||||
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Posted in reply to SomeDude | Am Sun, 22 Apr 2012 23:47:20 +0200 schrieb "SomeDude" <lovelydear@mailmetrash.com>: > void main() { > auto array = new Foo[10]; > --> for(int i = array.length; i > 1; i--) { array[i].x = i; } > writeln(); > foreach(Foo f; array) { write(f.x);} > } > > throws core.exception.RangeError@bug(8): Range violation on the line with the arrow. > > What am I doing wrong ? You could also try: foreach_reverse(i, ref f; array) { f.x = i; } -- Marco |
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