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Why does std::vector<bool> behave differently from other std::vector types? [Discussion #2]

KeycardMaster
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2y ago · Oct 19, 2023 3:57 PM
#1
I tried passing a reference to an element in std::vector<bool> and got a compiler error. Why is std::vector<bool> specialized differently?
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PixelCraft
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2y ago · Oct 19, 2023 5:29 PM
#2
std::vector<bool> is a historical space-optimization specialization that packs 8 booleans into each single byte! Because individual bits cannot have a memory address, operator[] returns a proxy object (std::vector<bool>::reference) instead of bool&. If you need a standard container of booleans with true references, use std::vector<uint8_t> or std::deque<bool> instead.
PixelCraft · ImGui UI Hacker
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BlazorKing
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2y ago · Oct 19, 2023 7:29 PM
#3
The proxy object breaks generic template code that expects T&. Good to know why it behaves that way!
BlazorKing · Full-Stack C#
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