Copying data is wasteful, mutating data is dangerous

Re:Copying data is wasteful, mutating data is dangerous by masklinn on Thursday January 09, 2020 @01:47PM (#22004154)

> As far as I know, only Rust, C++, and C give support at the type-checking level to denote which functions will modify the interior of their arguments.

1. C and C++ allow casting away constness, which may or may not be UB depending how the parameter is defined

2. Swift also provides this ability to an extent: struct parameters have to be flagged `inout` to be mutable

I'm sure there are others.

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Re:Copying data is wasteful, mutating data is dangerous by nwallin on Thursday January 09, 2020 @03:49PM (#22005534)

Rust can throw away constness in unsafe blocks, which carries the same caveat emptor that const_cast carries.

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Re:Copying data is wasteful, mutating data is dangerous by steveklabnik on Thursday January 09, 2020 @04:42PM (#22006190)

Only in certain circumstances, though.

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Re:Copying data is wasteful, mutating data is dangerous by gdxhyrd on Thursday January 09, 2020 @02:07PM (#22004350)

Casting away constness in C++ is something it is virtually never done, and has to be done very explicitly.

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Re:Copying data is wasteful, mutating data is dangerous by masklinn on Thursday January 09, 2020 @03:02PM (#22005025)

> https://github.com/search?q=const_cast&type=Code

We must have very different notions of "virtually never": https://github.com/search?q=const_cast&type=Code

> has to be done very explicitly.

That doesn't make it visible to the caller.

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