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March 06, 2007
Re: Bidimensional dynamic array problem
Frits van Bommel Wrote:

> orgoton wrote:
> > I have this
> > 
> > struct Vertex{
> > (...)
> > float z;
> > }
> > 
> > then:
> > Vertex vData[][];
> > 
> > Somewhere later:
> > vData.length=sizeX;
> > foreach(Vertex strip[]; vData[]) strip.length=sizeY;
> 
> foreach(inout Vertex[] strip; vData) strip.length = sizeY;
> or just:
> foreach(inout strip; vData) strip.length = sizeY;
> 
> Note: only the inout is significant, the rest is just nitpicking :P.
> If you don't specify 'inout', you're just modifying a local copy of the 
> element...
> 
> And IIRC something like "vData = new Vertex[][](sizeX, sizeY)" should 
> replace that entire code sequence, initializing the outer array to an 
> array of sizeX arrays of length sizeY.
> 
> > Here the array is initialized. So far, I think I haven't done anything illegal. (SizeX and SizeY are runtime values, ushort vars). So first I say how many strips I want, and next, I put in how many elements that strip will have.
> 
> You haven't done anything illegal, just something wrong ;).
> You haven't initialized the array the way you thought you did: it's just 
> an array of _empty_ dynamic arrays at this point.
> 
> > ulong m;
> > foreach (Vertex[] strip; vData)
> 
> (this loop doesn't require 'inout' since the array itself isn't 
> modified, just the data it references)
> 
> > {
> >       foreach (Vertex vertex; strip)
> 
> foreach(inout Vertex vertex; strip)
> (or: foreach(inout vertex; strip))
> 
> >       {
> >            file.read(vertex.height);
> >            m++;
> >       }
> > }
> > 
> > Here I read the values from a file. First, I select a strip, and then go through all the elements of that array and read their values. "m" is a counter to see how many elements where read.
> > 
> > The thing is, m=0 at the end of the loop. What did I do wrong?
> 
> Since you didn't initialize the elements of vData, their lengths are all 
> still zero. So your inner loop is never executed.


That did it! Thanks a lot. I feel illuminated :P
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