Confused on example in ScopedValueSetter docs – template args missing?

#1

Minor one, just saw this code snippet as example in the docs

int x = 1;
 
{
    ScopedValueSetter setter (x, 2);
 
    // x is now 2
}
 
// x is now 1 again
 
{
    ScopedValueSetter setter (x, 3, 4);
 
    // x is now 3
}
 
// x is now 4

Isn’t this some C++ 17 magic? I guess in pre-C++ 17 the template type has to be explicitly specified like
ScopedValueSetter<int> setter (...) – or did I miss something? :wink: Might be confusing to newcomers that copy & paste the example code!

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#2

This documentation hasn’t changed since it was introduced in January 2011 though… Maybe some old compilers were happy to deduce the template type from the arguments.

#3

Interesting!

At least clang refuses to compile this code with C++ 14 as language standard and according to cppreference class template deduction through the constructor is C++ 17: https://en.cppreference.com/w/cpp/language/class_template_argument_deduction

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