apply(3scm)

💅 apply(3scm) — call a procedure with a list of arguments

okay bestie, welcome to apply(3scm), straight out of the Scheme Programmer's Manual ✨. This one's lowkey iconic — it's the "I have my args in a list, don't @ me" procedure. Let's get into it 🫶

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🦋 LIBRARY

import it from whichever flavour of Scheme you're living in, queen:

(import (rnrs))                     ;R6RS
(import (rnrs base))                ;R6RS
(import (scheme r5rs))              ;R7RS
(import (scheme base))              ;R7RS

🌸 SYNOPSIS

(apply procedure obj ... pair)

that's the whole vibe. no notes 💅

💖 DESCRIPTION

so apply calls procedure — but instead of you handing it arguments one by one like a peasant, it takes the elements of this list:

(append (list obj ...) pair)

and feeds those in as the actual arguments. that's it. that's the whole procedure. obj ... is however many objects you wanna front-load, and pair is the list that gets tacked on the end 🎀

⭐ RETURN VALUES

apply hands you back exactly the values that procedure returned when it got called in the manner above. no extra seasoning, no middleman nonsense — just whatever came out 🔥

🎀 EXAMPLES

(nothing here in the original, bestie — the EXAMPLES section is empty. the real examples live down in APPLICATION USAGE, keep scrolling 👇)

✨ APPLICATION USAGE

okay so when do you actually reach for this? main character use case: you need to call a procedure but the set of arguments you're giving it isn't known ahead of time — so you can't just type them out. that's apply's whole moment 🙌

it can also do a cute lil "fold" over a list of items, but only if procedure can take an arbitrary number of arguments. like this:

(apply + (list 1 2 3 4)) => 10

ate. no cap. 💀

💜 RATIONALE

(empty in the original! a mysterious queen. nothing to report 🕵️‍♀️)

🌈 COMPATIBILITY

(also empty — dry text, this section. we move 💅)

👑 ERRORS

this procedure can raise exceptions with these condition types, so pay attention:

• &assertion (R6RS) — the wrong number of arguments got passed, or an argument was outside its domain. basically: you fumbled the args 😭
• R7RS — the assertions described above are errors. implementations may signal an error, extend the procedure's domain of definition to include such arguments, or fail catastrophically. yes, catastrophically. not a drill 💀🔥

🧚 SEE ALSO

(empty in the original — nothing to point you at, sadly 🥲)

🌸 STANDARDS

it's standing on business across all of these: R4RS, IEEE Scheme, R5RS, R6RS, R7RS. five for five, periodt 👑

🍓 HISTORY

(empty — the lore is lost to time 🙈)

🫶 AUTHORS

this page is part of the scheme-manpages project! it includes materials from the RnRS documents. more info lives at https://github.com/schemedoc/manpages/ — go show them love 💖

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and that's the whole page, bestie 🦋 this was apply(3scm), dated 2022-02-01, from the Scheme Programmer's Manual — mwah, go call some procedures 💅✨