hashtable-set!(3scm)

💅 hashtable-set!(3scm) — the one where you change an association in a hashtable

okay so bestie, welcome to the Scheme Programmer's Manual ✨ and honestly? this page is short and sweet and it's gonna change your whole day, no cap.

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🌸 NAME 🌸

hashtable-set! — change an association in a hashtable 🎀

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📚 LIBRARY 📚

import it one of these ways, iykyk:

(import (rnrs))                     ;R6RS
(import (rnrs hashtables))          ;R6RS

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✨ SYNOPSIS ✨

(hashtable-set! hashtable key obj)

that's it. three arguments. main character energy fr fr 💖

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💖 DESCRIPTION 💖

so what it does is it changes hashtable so that it associates key with obj — like, it either adds a brand new association, or it replaces whatever association was already there for key. it's giving "out with the old, in with the new" 🌈 and it literally does not care which one it's doing, it just handles it 💅

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🧚 IMPLEMENTATION NOTES 🧚

okay so lowkey this is important: calling this procedure can trigger growth of the hashtable, and when that happens it can require all keys to be hashed again 😭 like the whole squad gets re-hashed. just so you know. 🫶

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⭐ RETURN VALUES ⭐

returns unspecified values. that's it. nothing to see here, no cool little result to show off, it's just vibes 🦋

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🍓 EXAMPLES 🍓

here's the whole cute little scenario:

(define ht (make-eq-hashtable))
(hashtable-set! ht 'foo 'bar)
(hashtable-ref ht 'foo #f)   =>  bar

look at that. bar came back. ate. 👑

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🔥 COMPATIBILITY 🔥

this procedure is unique to R6RS — like, it's its thing. but similar procedures do exist in SRFI-69 and SRFI-125, so if you're slumming it in a different SRFI you're not totally stranded, bestie 💀

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🙈 ERRORS 🙈

this procedure can raise exceptions with these condition types:

• &assertion (R6RS) — this one hits when you passed the wrong number of arguments, or when an argument was outside its domain. specifically: hashtable should actually be a hashtable, and key should be in the domain of the hashtable's hash and equal functions. so like. use it right. 😭

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🦋 SEE ALSO 🦋

• make-hashtable(3scm)
• hashtable-ref(3scm)

(the holy trinity honestly 🎀)

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👑 STANDARDS 👑

R6RS. periodt. 💜

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🌈 HISTORY 🌈

this procedure first appeared in R6RS. and fun fact: an equivalent procedure already existed in SRFI-69 under the name hash-table-set!. so it's not even a new idea, it just got a glow-up ✨

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🧚 AUTHORS 🧚

this page is part of the scheme-manpages project. it includes materials from the RnRS documents. more information can be found at https://github.com/schemedoc/manpages/ 🫶

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no cap, that's the whole page. go forth and set some keys, bestie 💅

okay and finally, the cute little sign-off: this gem dropped on 2023-01-22, straight from the Scheme Programmer's Manual, and it's hashtable-set!(3scm) through and through 💖🎀✨