WolframLang: Loop

By Xah Lee. Date: . Last updated: .

Procedural Style Loop

WolframLang is a function language. However, it supports the traditional loop constructs such as for-loop, while-loop. In general, you should not use them, because they are slower and more complex.

If you need to exit by condition or with side-effects, use Do, Scan. Else, use functional programing to maintain structure. See • Create List (Table)Map, ScanRecursion

Do-loop

The Do function is similar to Table [see WolframLang: Create List (Table, Range)] , except it doesn't generate a list, it just return Null (if there is no Return), and you can use Return, Break, Continue, and Throw inside Do.

Do

Do[expr, n]
evaluate expr n times.
Do[Print[2], 4]
Do[expr, {i, iMax}]
evaluate expr with the variable i successively taking on the values 1 through iMax (in steps of 1).
Do[Print[n^2], {n, 4}]
(* 1 4 9 16 *) 
Do[expr, {i, iMin, iMax}]
start with iMin.
Do[expr, {i, iMin, iMax, di}]
use steps di.
Do[expr, {i, iMin, iMax, di}, {j, jMin, jMax, dj} etc]
Nested do-loop. For each i, loop over j, etc.
Do[Print[n,m], {n, 3}, {m, 2}]

(* 11 12 21 22 31 32 *) 
Do[expr, {i, {i1, i2, i3, etc}}}]
use the successive values i.
Do[Print[i], {i, {1, 3, 20}}]
(* 
1
3
20
*)

For-loop

For loop is basically never used in WolframLang, except in beginner code.

For

For[i = 1, i < 9, i++, Print[i]]

While-loop

While loop is basically never used in WolframLang, except in beginner code.

While

n = 1; While[n < 4, Print[n]; n++]

WolframLang Loop, Iteration, Recursion