Sum and product of an array: Difference between revisions

Perhaps better Babel:

<lang babel>main:

{ [2 3 5 7 11 13]

ar2ls dup cp

<- sum_stack ->

prod_stack

%d cr <<

%d cr << }

sum_stack:

{ { give

{ + }

{ depth 1 > }

do_while } nest }

prod_stack:

{ { give

{ * }

{ depth 1 > }

do_while } nest }</lang>

The nest operator creates a kind of argument-passing context -

it saves whatever is on Top-of-Stack (TOS), saves the old stack,

clears the stack and places the saved TOS on the new, cleared stack.

This permits a section to monopolize the stack. At the end of the nest

context, whatever is on TOS will be "passed back" to the original stack

which will be restored.

The depth operator returns the current depth of the stack.