find(3scm)

✨ find(3scm) ✨

okay bestie, so this is find from the Scheme Programmer's Manual — and honestly it's giving "where's my thing" energy in the best way possible 💅

💖 NAME 💖

find — search a list for an element that satisfies a predicate, and when it finds it? slay. returns it. periodt 🎀

🦋 LIBRARY 🦋

(import (rnrs))                     ;R6RS
(import (rnrs lists))               ;R6RS

🌸 SYNOPSIS 🌸

(find proc list)

⭐ DESCRIPTION ⭐

so here's the vibe: find takes proc and applies it to the elements of list in order — like, one at a time, no skipping, no chaos, very methodical queen behavior 👑

the moment proc returns a true value for an element, find immediately returns that element. no further searching. she's done. bye 🫶

but if proc returns #f for all the elements of the list? then find returns #f. tragic, but that's the rules 😭

one thing though: proc is always called in the same dynamic environment as find itself. no sneaky environment switching, iykyk.

and proc should accept one argument and return a single value. also — proc should not mutate list. hands off the list, bestie 🙈

🧚 IMPLEMENTATION NOTES 🧚

okay this part is for the people building it, but it's literally so important so listen up:

• the implementation must check that list is a chain of pairs up to the found element, or that it is indeed a list if no element is found.
• it should not check that it's a chain of pairs beyond the found element. like, mind your business past that point 💀
• the implementation must check the restrictions on proc to the extent performed by applying it as described.
• an implementation may check whether proc is an appropriate argument before applying it. optional flex, basically 💅

🌈 RETURN VALUES 🌈

returns a single value, which is either one of the elements of list, or #f. two possibilities, that's it, no plot twists 🍓

🔥 EXAMPLES 🔥

(find even? '(3 1 4 1 5 9))  =>  4
(find even? '(3 1 5 1 5 9))  =>  #f

see how the first one found that 4 and was like "found her 💖" and the second one searched the whole thing and came back with #f? relatable honestly 😭

💀 ERRORS 💀

this procedure can raise exceptions with the following condition types:

• &assertion (R6RS) — the wrong number of arguments was passed, or an argument was outside its domain. so like, if you pass the wrong stuff, she will let you know 🙈

👑 SEE ALSO 👑

• member(3scm)

🌸 STANDARDS 🌸

R6RS, SRFI-1 — certified, iconic, standards-approved ✨

🎀 HISTORY 🎀

this procedure is new in R6RS, which got it from SRFI-1. so basically it's an SRFI-1 baddie that got promoted to R6RS main character status 👑

💜 AUTHORS 💜

this page is part of the scheme-manpages project — it includes materials from the RnRS documents, and you can find more info at https://github.com/schemedoc/manpages/ 🫶

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and that's the whole page, bestie!! 🌟 dated 2022-03-27, from the scheme-manpages project, find(3scm) — go forth and search your lists, you've got this 💖✨🎀