Both of those are macros (basically special words that produce a
quotation), so when "called" they are first macro-expanded into a quotation
and then that quotation is called, with whatever stack effect it has.
IN: scratchpad 1 2 3 "%s %s %s" printf
1 2 3
IN: scratchpad [ "%s %s %s" printf ] infer
( x x x -- )
IN: scratchpad [ "%s %s %s" printf ] expand-macros
[
[ present ] 2 ndip [ " " ] 2 ndip [ present ] 1 ndip
[ " " ] 1 ndip [ present ] 0 ndip output-stream get
[ stream-write ] curry 5 napply
]
Maybe the article I wrote when developing it would help:
https://re-factor.blogspot.com/2011/08/printf.html
On Thu, Jan 18, 2018 at 4:32 AM, Alexander Ilin <ajs...@yandex.ru> wrote:
> Hello!
>
> There are two similar words: printf and sprintf. They have similar stack
> effects, but different behavior.
>
> MACRO: sprintf ( format-string -- result )
> leaves a string on stack
>
> MACRO: printf ( format-string -- quot )
> leaves nothing on stack despite the stack effect specified
>
> How come `printf` does'n obey its declared stack effect?
>
> ---=====---
> Александр
>
>
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