Built in function to count the number of bits set about emboss HOT 3 OPEN

Are you asking for a POPCOUNT function + a way to reinterpret_cast a bits to UInt, or something that would actually analyze the bits and only pay attention to known Flag fields?

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I was asking more for a std::popcount type approach.

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Adding $popcount should be straightforward: a 1-adic function that takes an integer argument. Min value is 0, max value is ciel(log2(input max val)), +1 if the input can be negative. Would need some #ifs in the C++ implementation to use std::popcount() or __builtin_popcount() where available, and fallback to a C++11 native implementation otherwise.

Internally, a bits field and a UInt field (also Flag, Int, Float, etc.) are treated similarly, so some equivalent of reinterpret_cast that basically says "pretend this field is this other type and read it out" should be doable. We would have to figure out a readable syntax -- there aren't many languages that let you cast pointers that way, so $reinterpret_cast<UInt>(field) might be the least-bad option.

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