Logo

Programming-Idioms

History of Idiom 7 > diff from v47 to v48

Edit summary for version 48 by :
[Haskell] Shorter, more idiomatic, less duplication
↷

Version 47

2016-02-17, 11:50:39

Version 48

2016-02-18, 16:57:56

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

Imports 
with Ada.Text_IO;
use Ada.Text_IO;
Imports 
with Ada.Text_IO;
use Ada.Text_IO;
Code 
for I in Items'Range loop
   X := Items (I);
   Put_Line (Integer'Image (I) & " " & Integer'Image (X));
end loop;
Code 
for I in Items'Range loop
   X := Items (I);
   Put_Line (Integer'Image (I) & " " & Integer'Image (X));
end loop;
Comments bubble
Assuming Items is an array of integers.
Comments bubble
Assuming Items is an array of integers.
Imports 
using System;
Imports 
using System;
Code 
for (int i = 0; i < items.Length; i++)
{
    Console.WriteLine("{0} {1}", i, items[i]);
}
Code 
for (int i = 0; i < items.Length; i++)
{
    Console.WriteLine("{0} {1}", i, items[i]);
}
Imports 
#include <iostream>
#include <vector>
Imports 
#include <iostream>
#include <vector>
Code 
for(const auto & item : items) {
  static auto idx = 0;
  std::cout << "Item " << idx++ << " = " << item << std::endl;
}
Code 
for(const auto & item : items) {
  static auto idx = 0;
  std::cout << "Item " << idx++ << " = " << item << std::endl;
}
Comments bubble
Uses the C++11 features "range based for loop" and "auto"
Comments bubble
Uses the C++11 features "range based for loop" and "auto"
Code 
mapM_ print (zip [0..] items)
Code 
mapM_ print (zip [0..] items)
Imports 
Classes, SysUtils
Imports 
Classes, SysUtils
Code 
var Iter:Integer;
    Items: array of TObject;
[...]
  for Iter := 0 to high(Items) do
    if assigned(Items[Iter]) then
      WriteLn(Format('Item %d = %s', [Iter, Items[Iter].ToString]));
Code 
var Iter:Integer;
    Items: array of TObject;
[...]
  for Iter := 0 to high(Items) do
    if assigned(Items[Iter]) then
      WriteLn(Format('Item %d = %s', [Iter, Items[Iter].ToString]));
Comments bubble
If you have an TObjects descendent, you can use the ToString method to get it as a String.
Comments bubble
If you have an TObjects descendent, you can use the ToString method to get it as a String.
Code 
items.forEach(function(val,idx,ary){
  console.log("index=" + idx + ", value=" + val);
});
Code 
items.forEach(function(val,idx,ary){
  console.log("index=" + idx + ", value=" + val);
});
Comments bubble
This is the "functional way" of iterating.
Comments bubble
This is the "functional way" of iterating.
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
Doc URL
https://golang.org/doc/effective_go.html#for
Doc URL
https://golang.org/doc/effective_go.html#for
Demo URL
http://play.golang.org/p/GH_8f06DX5
Demo URL
http://play.golang.org/p/GH_8f06DX5