hashtable-contains?(3scm)

💅 hashtable-contains? — Scheme Programmer's Manual (3scm)

okay so bestie, welcome to the Scheme Programmer's Manual page for hashtable-contains?. this one's short and sweet and honestly kind of a queen. let's get into it 🎀

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✨ NAME

hashtable-contains? — check if a key exists in a hashtable

like, does this table know your guy or not. that's the whole vibe check 🔍

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📚 LIBRARY

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

both of these get you the goods, no cap 💖

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🦋 SYNOPSIS

(hashtable-contains? hashtable key)

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🌸 DESCRIPTION

Returns #t if hashtable contains an association for key, #f otherwise.

that's it. that's the whole thing. yes-or-no, in-or-out, slay-or-nay 💅

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⭐ RETURN VALUES

Returns a single value; a boolean object. just one (1) little boolean, no extra baggage, we love a minimal icon ✨

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🍓 EXAMPLES

(let ((ht (make-eqv-hashtable)))
  (hashtable-set! ht (* 7 6) 'answer)
  (hashtable-contains? ht 42))
    => #t

the way (* 7 6) is literally 42... math ate that 🧮🔥

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👑 APPLICATION USAGE

This procedure provides a general for checking if hashtables contain certain keys. If the hashtable never has associations with booleans then another common solution is to use hashtable-ref(3scm) with #f as the default value.

ok so like — this is your general-purpose "is it in there?" tool 🫶. but heads up, bestie: if your hashtable never stores actual booleans, another popular move is calling hashtable-ref(3scm) with #f as the default, and reading the answer off that. just know the difference, iykyk 💀

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🌈 COMPATIBILITY

This procedure is unique to R6RS.

genuinely one of a kind. main character energy, no other standard can claim her 🔥

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💀 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.
• 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.

😭 "fail catastrophically" is right there in the spec and we are NOT calm about it. do not pass weird args, bestie. i'm begging 🙈

&assertion (R6RS)

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🧚 SEE ALSO

• hashtable-ref(3scm)

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🎀 STANDARDS

R6RS

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💜 HISTORY

This procedure first appeared in R6RS. An equivalent procedure can be found in SRFI-69 under the name hash-table-exists?.

so she debuted in R6RS, and if you're hanging out in SRFI-69 land you'll find her twin going by hash-table-exists?. same energy, different name, iconic either way 👑

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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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and that's the whole page, bestie!! this one's from the Scheme Programmer's Manual, dated 2023-01-121, filed under hashtable-contains?(3scm) — now go check your keys and slay 💖✨🌸