count

Count number of true booleans.

Can be used to implement one-hot / one-cold detector.

count([a], [b], [c], [d], [e], [f], [g], [h])
// a: 1st boolean
// b: 2nd boolean
// c: 3rd boolean
// d: 4th boolean
// e: 5th boolean
// f: 6th boolean
// g: 7th boolean
// h: 8th boolean

const xboolean = require('extra-boolean');

xboolean.count(true, true);
// → 2         ^     ^

xboolean.count(true, false);
// → 1         ^

xboolean.count(true, true, true, false);
// → 3         ^     ^     ^

xboolean.count(false, true, false, false);
// → 1                ^

References

• Parallel method: Bit Twiddling Hacks
• bit-twiddle: @mikolalysenko
• count-bits: @DenQ
• popcnt32: @emilbayes