Editing Iteration (section)

=== Implementations ===
[[Control flow#Loops |Loops]] constitute the most common language constructs for performing iterations. The following [[pseudocode]] "iterates" three times the line of code between begin & end through a ''for loop'', and uses the values of ''i'' as increments.

<syntaxhighlight lang="pascal">
a := 0
for i := 1 to 3 do       { loop three times }
begin
    a := a + i;          { add the current value of i to a }
end;
print(a);                { the number 6 is printed (0 + 1; 1 + 2; 3 + 3) }
</syntaxhighlight>

It is permissible, and often necessary, to use values from other parts of the program outside the bracketed block of statements, to perform the desired function.

[[Iterators]] constitute alternative language constructs to loops, which ensure consistent iterations over specific data structures. They can eventually save time and effort in later coding attempts. In particular, an iterator allows one to repeat the same kind of operation at each node of such a data structure, often in some pre-defined order.

[[Iteratees]] are purely functional language constructs, which accept or reject data during the iterations.