accumulate! ( ... seq identity quot: ( ... prev elt -- ... next ) -- ... final seq )
Factor handbook > The language > Collections > Sequence operations > Destructive sequence operations

Prev:map! ( ... seq quot: ( ... elt -- ... newelt ) -- ... seq )
Next:accumulate*! ( ... seq identity quot: ( ... prev elt -- ... next ) -- ... seq )


Vocabulary
sequences

Inputs and outputs
seqa mutable sequence
identityan object
quota quotation with stack effect ( ... prev elt -- ... next )
finalthe final result


Word description
Combines successive elements of the sequence using a binary operation, and outputs the original sequence of intermediate results, together with the final result.

The first element of the new sequence is identity. Then, on the first iteration, the two inputs to the quotation are identity, and the first element of the old sequence. On successive iterations, the first input is the result of the previous iteration, and the second input is the corresponding element of the old sequence.

When given the empty sequence, outputs the same empty sequence together with the identity.

Errors
Throws an error if the sequence is immutable, or the sequence cannot hold elements of the type output by quot.

Side effects
Modifies seq

Examples
USING: math prettyprint sequences ; { 2 2 2 2 2 } 0 [ + ] accumulate! . .
{ 0 2 4 6 8 } 10


Notes
May be named scan or prefix sum in other languages.

See also
accumulate, accumulate-as, accumulate*, accumulate*!, accumulate*-as

Definition


: accumulate!
( ... seq identity quot: ( ... prev elt -- ... next ) -- ... final seq )
(accumulate) map! ; inline