Do

Evaluates an expression repeatedly, for its side effects, and returns Nothing.

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Do(body, n)Evaluates

body

n

times, with no loop variable.

Do(body, {i, imax})Evaluates

body

with

i

running

1, 2, \dots, imax

Do(body, {i, imin, imax})Evaluates

body

with

i

running

imin, imin+1, \dots, imax

Do(body, {i, imin, imax, di})Evaluates

body

with

i

running

imin, imin+di, \dots

up to (or down to, for

di<0

)

imax

Typed signatures

Type	Package	Applies
`(any, any) -> any`	`combinatorics`	always

Domain: Collections

Details

Always returns $Nothing$ — this library's stand-in for Wolfram's $Null$ (see the $Nothing: Null$ entry in @enumeratio/wolfram's SYMBOLS map).
$i$ , when named, is a fresh local for the whole call, the same way Module's locals are — it does not leak, and does not clobber an outer binding of the same name.
Bounds and step are integers only; Wolfram additionally allows real-valued iterators.
The examples below place the $Do$ call inside a $List$ alongside its surrounding statements — the $Nothing$ it returns simply vanishes from that $List$ (compute-engine's own behavior for $Nothing$ , matching Wolfram), which is why each result has one fewer entry than statements written.

Examples

Basic #

sum 1 through 5 with a named loop variable

\bigl\lbrack\mathrm{total}\coloneq0, \mathrm{Do}(\mathrm{total}\coloneq\mathrm{total}+k, \bigl\lbrack k, 1, 5\bigr\rbrack), \mathrm{total}\bigr\rbrack

Out

\bigl\lbrack0, 15\bigr\rbrack

Do(body, n) repeats with no loop variable

\bigl\lbrack\mathrm{count}\coloneq0, \mathrm{Do}(\mathrm{count}\coloneq\mathrm{count}+1, 4), \mathrm{count}\bigr\rbrack

Out

\bigl\lbrack0, 4\bigr\rbrack

Applications #

\mathrm{Reap}(\mathrm{Do}(\mathrm{If}(\mathrm{IsPrime}(2^{n}-1), \mathrm{Sow}(n)), \bigl\lbrack n, 100\bigr\rbrack))[2, 1]

Out

\bigl\lbrack2, 3, 5, 7, 13, 17, 19, 31, 61, 89\bigr\rbrack

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