bitwise-bit-count(3scm)

📦 version 0-unstable-2024-02, in nixpkgs unstable

🎀 NAME 🎀

bitwise-bit-count — population count, bestie ✨

okay so this is the bitwise-bit-count(3scm) page from the Scheme Programmer's Manual, and we're gonna get you comfy with it 💖

📚 LIBRARY 📚

the imports are giving very R6RS, no cap:

(import (rnrs))                     ;R6RS
(import (rnrs arithmetic bitwise))  ;R6RS
(import (rnrs arithmetic fixnums))  ;R6RS

🪄 SYNOPSIS 🪄

(bitwise-bit-count ei)
(fxbit-count fx)

💖 DESCRIPTION 💖

If the argument is non-negative, this procedure returns the number of 1 bits in its two's complement representation. slay.

Otherwise, it returns the result of this computation, exactly:

(bitwise-not (bitwise-bit-count (bitwise-not ei)))

like, that's the whole vibe 🦋

🌟 RETURN VALUES 🌟

Returns a single exact integer object. one exact integer object, periodt 💅

✨ EXAMPLES ✨

these examples are iconic, honestly:

(bitwise-bit-count #b1)
          => 1

(bitwise-bit-count #b1000)
          => 1

(bitwise-bit-count #b1001)
          => 2

(bitwise-bit-count #b-1001)
          => -2

🛠️ APPLICATION USAGE 🛠️

This procedure is used to compute the Hamming distance. It's also used in Hash Array Mapped Tries and other applications. iykyk 💜

🧩 COMPATIBILITY 🧩

This procedure is new in R6RS. SRFI-151 has the similar procedure bit-count.

💀 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. For fxbit-count the argument must be a fixnum. yes, that includes the fixnum vibe check 🔥

👀 SEE ALSO 👀

📜 STANDARDS 📜

R6RS 👑

🕰️ HISTORY 🕰️

This procedure can be implemented with the popcount procedure in x86-64 processors. This instruction appeared even in some early computers like the IBM Stretch (1961). history class but make it bits 😭

🫶 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/. 💖

xoxo, your Scheme bestie 🫶 — source/version: Scheme Programmer's Manual, bitwise-bit-count(3scm), dated 2021-03-08. bye bestie! 🎀

📦 where this page comes from