4 ms·

I hate const char. This notation sucks. Is it (const char) or const (char*)? i.e. is it a pointer to a char but the memory address it points to is

by dheera 3y ago

I hate const char*. This notation sucks. Is it (const char)* or const (char*)? i.e. is it a pointer to a char but the memory address it points to is const, or is it a variable pointer that points to a const char.

10000truths 3y ago
It is the former, a pointer to a const char. A const pointer to char would be qualified as: char* const
- Koshkin 3y ago
  const char* const f() const is the best!
ndesaulniers 3y ago
I think const char * and char * const are obvious (whichever the const keyword is closest to). That rule of thumb doesn't work though for char const * or char * const * though.
- dheera 3y ago
  > char * const Oof no I HATE this. I also hate it when people write char *a; because the type is char* (i.e. pointer to a char) and the name of the variable is a.
  - moregrist 3y ago
    `char * const a` is a different type from `const char *a`. In the first, the variable `a` is const, but `*a` is not const. That is, you cannot change the value of `a` but you can change what it points to. In the second `a` is not const, but `*a` is. That is, you can change `a` but you cannot change the value it points to. I feel that your confusion is tied up in not understanding how C and C++ type declarations work, as is your insistence on `char* a`. Dennis Ritchie (the C language designer) intended it to be written as `char *a` and talked about this at length over the years as an important design decision: variable declaration follows _usage_, so it’s `char *a` because the type of `*a` is `char`. For better or worse, Stroustrup took this design decision into C++. Sure both will parse in this simple case, but keeping this in mind is also the way that more complex declarations make sense.
  - Dylan16807 3y ago
    > because the type is char* (i.e. pointer to a char) and the name of the variable is a. But it's not. char *a, b; The type you are assigning is just char. The * only affects a.
- eMSF 3y ago
  A lot of folks write char const * (and T const& in C++), and the "rule of thumb" is to read the declaration right to left. In this case, pointer (to) const char. Works also with multiple consts or levels of indirection.
joatmon-snoo 3y ago
This explanation from isocpp is the one that has always guided me: Read the pointer declarations right-to-left. * const X* p means “p points to an X that is const”: the X object can’t be changed via p. * X* const p means “p is a const pointer to an X that is non-const”: you can’t change the pointer p itself, but you can change the X object via p. * const X* const p means “p is a const pointer to an X that is const”: you can’t change the pointer p itself, nor can you change the X object via p. And, oh yea, did I mention to read your pointer declarations right-to-left? https://isocpp.org/wiki/faq/const-correctness#const-ptr-vs-ptr-const https://isocpp.org/wiki/faq/const-correctness#const-ptr-vs-p...

I hate const char*. This notation sucks. Is it (const char)* or const (char*)? i.e. is it a pointer to a char but the memory address it points to is

by dheera 3y ago

10000truths 3y ago

It is the former, a pointer to a const char. A const pointer to char would be qualified as: char* const

Koshkin 3y ago
const char* const f() const is the best!

ndesaulniers 3y ago

I think const char * and char * const are obvious (whichever the const keyword is closest to). That rule of thumb doesn't work though for char const * or char * const * though.

dheera 3y ago
> char * const Oof no I HATE this. I also hate it when people write char *a; because the type is char* (i.e. pointer to a char) and the name of the variable is a.
- moregrist 3y ago
  `char * const a` is a different type from `const char *a`. In the first, the variable `a` is const, but `*a` is not const. That is, you cannot change the value of `a` but you can change what it points to. In the second `a` is not const, but `*a` is. That is, you can change `a` but you cannot change the value it points to. I feel that your confusion is tied up in not understanding how C and C++ type declarations work, as is your insistence on `char* a`. Dennis Ritchie (the C language designer) intended it to be written as `char *a` and talked about this at length over the years as an important design decision: variable declaration follows _usage_, so it’s `char *a` because the type of `*a` is `char`. For better or worse, Stroustrup took this design decision into C++. Sure both will parse in this simple case, but keeping this in mind is also the way that more complex declarations make sense.
- Dylan16807 3y ago
  > because the type is char* (i.e. pointer to a char) and the name of the variable is a. But it's not. char *a, b; The type you are assigning is just char. The * only affects a.
eMSF 3y ago
A lot of folks write char const * (and T const& in C++), and the "rule of thumb" is to read the declaration right to left. In this case, pointer (to) const char. Works also with multiple consts or levels of indirection.

joatmon-snoo 3y ago

This explanation from isocpp is the one that has always guided me: Read the pointer declarations right-to-left. * const X* p means “p points to an X that is const”: the X object can’t be changed via p. * X* const p means “p is a const pointer to an X that is non-const”: you can’t change the pointer p itself, but you can change the X object via p. * const X* const p means “p is a const pointer to an X that is const”: you can’t change the pointer p itself, nor can you change the X object via p. And, oh yea, did I mention to read your pointer declarations right-to-left? https://isocpp.org/wiki/faq/const-correctness#const-ptr-vs-ptr-const https://isocpp.org/wiki/faq/const-correctness#const-ptr-vs-p...