Re: foreach( i, e; a) vs ndslice

[Ilya Yaroshenko via Digitalmars-d-learn]

On Monday, 18 January 2016 at 23:33:53 UTC, Jay Norwood wrote:

I'm playing with the example below.  I noticed a few things.
1. The ndslice didn't support the extra index, i, in the 
foreach, so had to add extra i,j.
2. I couldn't figure out a way to use sliced on the original 
'a' array.  Is slicing only available on 1 dim arrays?
3. Sliced parameter order is different than multi-dimension 
array dimension declaration.


import std.stdio;
import std.experimental.ndslice.slice;

void main() {
int[4][5] a = new int[20];
foreach(i,ref r; a){
foreach(j,ref c; r){
c= i+j;
writefln("a(%d,%d)=%s",i,j,c);
}
}
writefln("a=%s",a);

auto b = new int[20].sliced(5,4);

int i=0;
foreach( ref r; b){
int j=0;
foreach( ref c; r){
c= i+j;
writefln("b(%d,%d)=%s",i,j,c);
j++;
}
i++;
}
writefln("b=%s",b);

}


Hi,

1. You can use std.range.enumerate or just use a normal foreach:
  foreach(i; 0..slice.length!0)
  {
/// use slice[i] ...
  }
2. Yes (A 2D D array is an array of arrays, so slice would be a 
slice composed of arrays)

3. Order is correct:

void main() {
auto a = new long[][](5, 4);
auto b = new long[20].sliced(5, 4);
foreach(i, ref r; a) {
foreach(j, ref c; r) {
c = i+j;
b[i, j] = c;
writefln("a(%d,%d)=%s", i, j, c);
writefln("b(%d,%d)=%s", i, j, b[i, j]);
}
}
writefln("a=%s",a);
writefln("b=%s",b);
}

Ilya

foreach( i, e; a) vs ndslice

[Jay Norwood via Digitalmars-d-learn]

I'm playing with the example below.  I noticed a few things.
1. The ndslice didn't support the extra index, i, in the foreach, 
so had to add extra i,j.
2. I couldn't figure out a way to use sliced on the original 'a' 
array.  Is slicing only available on 1 dim arrays?
3. Sliced parameter order is different than multi-dimension array 
dimension declaration.


import std.stdio;
import std.experimental.ndslice.slice;

void main() {
int[4][5] a = new int[20];
foreach(i,ref r; a){
foreach(j,ref c; r){
c= i+j;
writefln("a(%d,%d)=%s",i,j,c);
}
}
writefln("a=%s",a);

auto b = new int[20].sliced(5,4);

int i=0;
foreach( ref r; b){
int j=0;
foreach( ref c; r){
c= i+j;
writefln("b(%d,%d)=%s",i,j,c);
j++;
}
i++;
}
writefln("b=%s",b);

}