CODEWITHSUNDEEP
c++c++11
xdevel2000
xdevel2000

Reputation: 21364

Range for syntax

When I write something like this:

int data[] = {10,44,56,78,8};      
int i = 0;
for(int element : data)
   ...

that for is then translated by the compiler in a regular for? is that for only a syntactic sugar?

Upvotes: 1

Views: 249

Answers (1)

Joseph Mansfield
Joseph Mansfield

Reputation: 110658

The standard defines the range-based for statement to be equivalent to:

{
  auto && __range = range-init;
  for ( auto __begin = begin-expr,
             __end = end-expr;
        __begin != __end;
        ++__begin ) {
    for-range-declaration = *__begin;
    statement
  }
}

In your case, range-init is (data), begin-expr is __range, end-expr is __range + 5, for-range-declaration is int element and statement is .... That is, if we substitute all of these, your for loop is equivalent to:

{
  auto && __range = (data);
  for ( auto __begin = __range,
             __end = __range + 5;
        __begin != __end;
        ++__begin ) {
    int element = *__begin;
    ...
  }
}

Whether this translation is actually done by the compiler is an implementation detail. The only thing you can guarantee is that your code will be equivalent to the above code.

Upvotes: 7

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