Idiom #6 Iterate over list values

Do something with each item x of the list (or array) items, regardless indexes.

Idiom #7 Iterate over list indexes and values

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

Idiom #286 Iterate over characters of a string

Print a line "Char i is c" for each character c of the string s, where i is the character index of c in s (not the byte index).

Make sure that multi-byte characters are properly handled, and count for a single character.

Idiom #143 Iterate alternatively over two lists

Iterate alternatively over the elements of the lists items1 and items2. For each iteration, print the element.

Explain what happens if items1 and items2 have different size.

Idiom #242 Iterate over a set

Call a function f on each element e of a set x.

Idiom #13 Iterate over map keys and values

Access each key k with its value x from an associative array mymap, and print them.

Traversing each key and each associated object of mymap

Idiom #113 Iterate over map entries, ordered by values

Print each key k with its value x from an associative array mymap, in ascending order of x.
Multiple entries may exist for the same value x.

Idiom #112 Iterate over map entries, ordered by keys

Print each key k with its value x from an associative array mymap, in ascending order of k.

Idiom #141 Iterate in sequence over two lists

Iterate in sequence over the elements of the list items1 then items2. For each iteration print the element.

Idiom #83 Regex with character repetition

Declare the regular expression r matching the strings "http", "htttp", "httttp", etc.

Idiom #332 List of the keys of a map

Create the list k containing all the keys of the map m

Idiom #257 Traverse list backwards

Print each index i and value x from the list items, from the last down to the first.

Idiom #42 Continue outer loop

Print each item v of list a which is not contained in list b.
For this, write an outer loop to iterate on a and an inner loop to iterate on b.

Control flow jumping back to the beginning of the outermost loop

Idiom #43 Break outer loop

Look for a negative value v in 2D integer matrix m. Print it and stop searching.

Control flow jumping forward after the end of the outermost loop

Idiom #71 Echo program implementation

Basic implementation of the Echo program: Print all arguments except the program name, separated by space, followed by newline.
Skip the first argument if necessary, concatenate arguments as strings, append newline and print it to stdout.

Idiom #284 Create a zeroed list of integers

Create a new list a (or array, or slice) of size n, where all elements are integers initialized with the value 0.

Idiom #136 Remove all occurrences of a value from a list

Remove all occurrences of the value x from list items.
This will alter the original list or return a new list, depending on which is more idiomatic.

Idiom #2 Print Hello 10 times

Loop to execute some code a constant number of times

Idiom #316 Count occurrences in a list

Determine the number c of elements in the list x that satisfy the predicate p.

Idiom #222 Find the first index of an element in list

Set i to the first index in list items at which the element x can be found, or -1 if items does not contain x.