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Programming-Idioms

History of Idiom 7 > diff from v30 to v31

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Version 30

2015-10-27, 03:02:18

Version 31

2015-10-29, 14:05:11

Idiom #7 Iterate over list indexes and values

Print each index i with its value x from an array-like collection items

Idiom #7 Iterate over list indexes and values

Print each index i with its value x from an array-like collection items

Code 
items.asMap().forEach((i, value) {
  print('index=$i, value=$value');
});
Code 
items.asMap().forEach((i, value) {
  print('index=$i, value=$value');
});
Comments bubble
An alternative, but not really idiomatic.
Comments bubble
An alternative, but not really idiomatic.
Code 
var Iter:Integer;
    Items: array of String;
[..]
  for Iter := 0 to high(Items) do
    WriteLn('Item ', Iter, ' = ', Items[Iter]);
Code 
var Iter:Integer;
    Items: array of String;
[..]
  for Iter := 0 to high(Items) do
    WriteLn('Item ', Iter, ' = ', Items[Iter]);
Imports 
import std.stdio;
Imports 
import std.stdio;
Code 
foreach(i, x; items)
{
   writefln("%s: %s", i, x);
}
Code 
foreach(i, x; items)
{
   writefln("%s: %s", i, x);
}
Comments bubble
use 'ref' on the item variable 'x' to access by reference
Comments bubble
use 'ref' on the item variable 'x' to access by reference
Code 
for (final T x : items)
    System.out.println(x);
Code 
for (final T x : items)
    System.out.println(x);
Comments bubble
Solution if the index is irrelevant.
Comments bubble
Solution if the index is irrelevant.
Code 
for (int i = 0; i < items.size(); i++) {
    T x = items.get(i);
    System.out.printf("Item %d = %s%n", i, x);
}
Code 
for (int i = 0; i < items.size(); i++) {
    T x = items.get(i);
    System.out.printf("Item %d = %s%n", i, x);
}
Comments bubble
Solution if the list is a List.
Comments bubble
Solution if the list is a List.
Code 
for (int i = 0; i < items.length; i++) {
    T x = items[i];
    System.out.printf("Item %d = %s%n", i, x);
}
Code 
for (int i = 0; i < items.length; i++) {
    T x = items[i];
    System.out.printf("Item %d = %s%n", i, x);
}
Comments bubble
Solution if the list is an array.
Comments bubble
Solution if the list is an array.
Code 
items.each_index do |i| 
	puts "Item #{i} = #{items[i]}"
end
Code 
items.each_index do |i| 
	puts "Item #{i} = #{items[i]}"
end
Comments bubble
See also the one-liner Ruby solution
Comments bubble
See also the one-liner Ruby solution
Code 
int i;
for(i=0 ; i<n ; i++){
  T x = items[i];
  printf("Item %d = %s\n", i, toString(x) );
}
Code 
int i;
for(i=0 ; i<n ; i++){
  T x = items[i];
  printf("Item %d = %s\n", i, toString(x) );
}
Comments bubble
The loop variable i is the index. Inside the loop, access the value with items[i]
Comments bubble
The loop variable i is the index. Inside the loop, access the value with items[i]
Imports 
import "fmt"
Imports 
import "fmt"
Code 
for i, x := range items {
    fmt.Printf("Item %d = %v \n", i, x )
}
Code 
for i, x := range items {
    fmt.Printf("Item %d = %v \n", i, x )
}
Comments bubble
The range clause gives you index and value at the same time as loop variables
Comments bubble
The range clause gives you index and value at the same time as loop variables