Tell me the truth ...
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Well there are containers that store booleans in single bits (e.g.
std::vector<bool>- which was famously a big mistake).But in the general case you don't want that because it would be slower.
Why is this a big mistake? I’m not a c++ person
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Why is this a big mistake? I’m not a c++ person
The mistake was that they created a type that behaves like an array in every case except for
bool, for which they created a special magical version that behaves just subtly different enough that it can break things in confusing ways. -
The mistake was that they created a type that behaves like an array in every case except for
bool, for which they created a special magical version that behaves just subtly different enough that it can break things in confusing ways.Could you provide an example?
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This reminds me that I actually once made a class to store bools packed in uint8 array to save bytes.
Had forgotten that. I think i have to update the list of top 10 dumbest things i ever did.
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Apart from dynamically typed languages which need to store the type with the value
You know that depending on what your code does, the same C that people are talking upthread doesn't even need to allocate memory to store a variable, right?
How does that work?
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Wait till you here about every ascii letter. . .
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Wait till you here about every ascii letter. . .
what about them?
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what about them?
Ascii needs seven bits, but is almost always encoded as bytes, so every ascii letter has a throwaway bit.
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Ascii needs seven bits, but is almost always encoded as bytes, so every ascii letter has a throwaway bit.
Let's store the boolean there then!!
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Wait until you hear about alignment
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No it isn't. All statically typed languages I know of use a byte. Which languages store it in an entire 32 bits? That would be unnecessarily wasteful.
It's not wasteful, it's faster. You can't read one byte, you can only read one word. Every decent compiler will turn booleans into words.
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Wait until you hear about alignment
The alignment of the language and the alignment of the coder must be similar on at least one metric, or the coder suffers a penalty to develop for each degree of difference from the language's alignment. This is penalty stacks for each phase of the project.
So, let's say that the developer is a lawful good Rust
zealotPaladin, but she's developing in Python, a language she's moderately familiar with. Since Python is neutral/good, she suffers a -1 penalty for the first phase, -2 for the second, -3 for the third, etc. This is because Rust (the Paladin's native language) is lawful, and Python is neutral (one degree of difference from lawful), so she operates at a slight disadvantage. However, they are both "good", so there's no further penalty.The same penalty would occur if using C, which is lawful neutral - but the axis of order and chaos matches, and there is one degree of difference on the axis of good and evil.
However, if that same developer were to code in Javascript (chaotic neutral), it would be at a -3 (-6, -9...) disadvantage, due to 2 and 1 degree of difference in alignment, respectively.
Malbolge (chaotic evil), however, would be a -4 (-8, -12) plus an inherent -2 for poor toolchain availability.
..hope this helps. have fun out there!
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Let's store the boolean there then!!
That boolean can indicate if it's a fancy character, that way all ASCII characters are themselves but if the boolean is set it's something else. We could take the other symbol from a page of codes to fit the users language.
Or we could let true mean that the character is larger, allowing us to transform all of unicode to a format consisting of 8 bits parts. -
It's not wasteful, it's faster. You can't read one byte, you can only read one word. Every decent compiler will turn booleans into words.
You can’t read one byte
lol what. You can absolutely read one byte: https://godbolt.org/z/TeTch8Yhd
On ARM it's
ldrb(load register byte), and on RISC-V it'slb(load byte).Every decent compiler will turn booleans into words.
No compiler I know of does this. I think you might be getting confused because they're loaded into registers which are machine-word sized. But in memory a
boolis always one byte. -
Could you provide an example?
The biggest problem is that each element doesn't have a unique memory address; iterators aren't just pointers.
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things that store it as word size for alignment purposes (most common afaik), things that pack multiple books into one byte (normally only things like bool sequences/structs), etc
things that store it as word size for alignment purposes
Nope. bools only need to be naturally aligned, so 1 byte.
If you do
struct SomeBools { bool a; bool b; bool c; bool d; };its 4 bytes.
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How does that work?
I think he's talking about if a variable only exists in registers. In which case it is the size of a register. But that's true of everything that gets put in registers. You wouldn't say
uint16_tis word-sized because at some point it gets put into a word-sized register. That's dumb. -
things that store it as word size for alignment purposes
Nope. bools only need to be naturally aligned, so 1 byte.
If you do
struct SomeBools { bool a; bool b; bool c; bool d; };its 4 bytes.
sure, but if you have a single bool in a stack frame it's probably going to be more than a byte. on the heap definitely more than a byte
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You can’t read one byte
lol what. You can absolutely read one byte: https://godbolt.org/z/TeTch8Yhd
On ARM it's
ldrb(load register byte), and on RISC-V it'slb(load byte).Every decent compiler will turn booleans into words.
No compiler I know of does this. I think you might be getting confused because they're loaded into registers which are machine-word sized. But in memory a
boolis always one byte.Sorry, but you're very confused here.
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This reminds me that I actually once made a class to store bools packed in uint8 array to save bytes.
Had forgotten that. I think i have to update the list of top 10 dumbest things i ever did.
Ah, the creator od std::vector<bool>?
