hashtable-entries(3scm)

💅 hashtable-entries — get the entries in the hashtable as two vectors

okay so real talk, this page is hashtable-entries(3scm) from the Scheme Programmer's Manual, and it's honestly such a vibe. it's a tiny little procedure that hands you your whole hashtable on a platter — no cap. let's get into it 🫶

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✨ NAME ✨

hashtable-entries — get the entries in the hashtable as two vectors 🎀

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📚 LIBRARY 📚

bestie you gotta import it first, okay? like so:

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

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🌸 SYNOPSIS 🌸

(hashtable-entries hashtable)

one procedure, one argument, that's the whole thing. iconic behavior honestly 💅

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💖 DESCRIPTION 💖

so you hand it a hashtable, and it gives you back a vector of the keys in that hashtable and a vector of the corresponding values. like, both at once. two vectors. one call. we love efficiency 🦋

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⭐ RETURN VALUES ⭐

it returns two values — two vectors of equal length. that's it, that's the return. two vectors, same length, matching up (well… in some matching order, keep reading 👀). 💜

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🎀 EXAMPLES 🎀

here's the moment you've been waiting for, the example, she's gorgeous:

(let ((h (make-eqv-hashtable)))
  (hashtable-set! h 1 'one)
  (hashtable-set! h 2 'two)
  (hashtable-set! h 3 'three)
  (hashtable-entries h))
  => #(1 2 3)
     #(one two three)
          ; entries may be in different order

⚠️ ok so peep that comment at the bottom: entries may be in different order. do NOT hardcode your assumptions about ordering, bestie, that's an L waiting to happen 😭

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🌈 APPLICATION USAGE 🌈

reach for this when you're iterating over the entries of a hashtable in an indeterminate order, or when you just need all the associated values from a hashtable. like, all of them. at once. slay 🧚

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🔥 RATIONALE 🔥

ok so why does this exist when you could do it other ways? because: if a program needs all entries in a hashtable, this procedure is significantly faster than using hashtable-keys(3scm) together with hashtable-ref(3scm) for each key — the reason being it does not need to use the hash and equal functions. efficiency queen 👑✨

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🦋 COMPATIBILITY 🦋

this procedure is unique to R6RS — main character energy, she doesn't exist elsewhere. but if you want an equivalent, you can find one in SRFI-125 under the name hash-table-entries. so like, cousins basically 🫶

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💀 ERRORS 💀

it can raise exceptions with the following condition types:

• &assertion (R6RS) — the wrong number of arguments was passed, or an argument was outside its domain. 🙈

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🌟 SEE ALSO 🌟

• hashtable-keys(3scm)

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⭐ STANDARDS ⭐

R6RS — periodt.

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🧚 HISTORY 🧚

this procedure first appeared in R6RS. that's the whole origin story, no further lore 😌

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👑 AUTHORS 👑

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

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so yeah, that's the whole page 🍓 this lil writeup is from the scheme-manpages crew, dated 2023-01-22, and that's hashtable-entries(3scm) — go forth and grab your vectors, bestie 💅✨🌸