char=?(3scm)

💅 char=?(3scm) — ok so bestie, let's talk characters

Welcome to the Scheme Programmer's Manual entry for char=?(3scm), aka the character comparison girlies 💖 no cap, these five procedures are about to be your new faves.

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✨ NAME ✨

char=?, char<?, char>?, char<=?, char>=? — character comparison, periodt 🎀

📚 LIBRARY 📚

Pick your import, bestie — there's literally one for every era:

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

🦋 SYNOPSIS 🦋

(char=? char char char ...)
(char<? char char char ...)
(char>? char char char ...)
(char<=? char char char ...)
(char>=? char char char ...)

Okay so the vibe check here: every single one takes char after char after char … like a whole group chat of characters 📱✨

🌸 DESCRIPTION 🌸

So here's the tea ☕ — these procedures return #t if the results of passing their arguments to char->integer are, respectively:

• equal → char=?
• monotonically increasing → char<?
• monotonically decreasing → char>?
• monotonically nondecreasing → char<=?
• monotonically nonincreasing → char>=?

…and #f otherwise. Simple as that, iykyk 💅

And in R6RS systems, these procedures impose a total ordering on the set of characters according to their Unicode scalar values. Iconic behavior only 👑

⭐ RETURN VALUES ⭐

Returns a single boolean value. That's it, that's the whole return. #t or #f, no in-between, no situationships 💀

🔥 EXAMPLES 🔥

(char<? #\z #\ß)  =>  #t
(char<? #\z #\Z)  =>  #f

Not the lowercase z losing to ß — the Unicode scalar value said what it said 🫶

🌈 COMPATIBILITY 🌈

Okay so both R6RS and R7RS define the order based on the Unicode scalar values of characters, but heads up: R7RS does not require full Unicode support and also permits non-Unicode characters. So like, your mileage may vary depending on your implementation, ngl 🙈

These procedures exist in R5RS and earlier reports too, but plot twist: they were only required to support two arguments. Two!! 😭 So if you're going way back, keep that in mind.

And IEEE Scheme uses the ≤ and ≥ characters instead of <= and >= in the procedure entries — but like, that's probably a typo. Not me defending them, that's literally what the docs say 💀

💀 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, count your args bestie, and don't be handing over anything that isn't a character ✋
• 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.

fr fr "fail catastrophically" is right there in the spec. Like, that's not me being dramatic, that's the actual wording. Be careful out there 🫣

🧚 SEE ALSO 🧚

• char-ci=?(3scm) — the case-insensitive bestie, go show her some love 💜

👑 STANDARDS 👑

R4RS, IEEE Scheme, R5RS, R6RS, R7RS — she's been around, she's got range, she's literally a legacy icon ⭐

🍓 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 cutie dropped on 2021-02-20 as part of char=?(3scm) from the Scheme Programmer's Manual — stay slay, stay sorted, and may all your characters be monotonically increasing 🌸✨🦋