Zekfad/cpp-const-correctness-note.md

## cpp-const-correctness-note.md

      
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              cpp-const-correctness-note.md
            
          
      Expression
      Explanation
      
Can change p?


Can change *p?


const X * p
X const * p
  
  
p points to an X that is const.
  
  
+
  
  
-
  

X * const p
  
  
p is a const pointer to an X that is non-const.
  
  
-
  
  
+
  

const X * const p
X const * const p
  
  
p is a const pointer to an X that is const.
  
  
-
  
  
-
  

const X& r
X const& r
  
  
r is a reference to an X that is const.
It means r aliases an X object, but you can’t change that X object via r.
  
  
-
  
  
Not appliable
  

X& const r

  
Don't do it:  it is nonsense.
r is a const reference to an X.
That is redundant — references are always const.
X& const r is functionally equivalent to X& r.
  
  
+
  
  
Not appliable
Expression	Explanation	Can change `p`?	Can change `*p`?
const X * p X const * p	`p` points to an `X` that is `const`.	+	-
X * const p	`p` is a `const` pointer to an `X` that is non-`const`.	-	+
const X * const p X const * const p	`p` is a `const` pointer to an `X` that is `const`.	-	-
const X& r X const& r	`r` is a reference to an `X` that is `const`. It means `r` aliases an `X` object, but you can’t change that `X` object via `r`.	-	Not appliable
~~X& const r~~	Don't do it: it is nonsense. `r` is a `const` reference to an `X`. That is redundant — references are always `const`. `X& const r` is functionally equivalent to `X& r`.	+	Not appliable