[HH] c++ strings?

[Greg London]

hm, once I use pass by reference, I have to use "const" or I get a compile
error.

int main ()
{
  Note("hello world\n");
  return 0;
}


void Note( string &msg){
	_say("Note: "+msg);
}

The error is:

hello.cpp:20: error: invalid initialization of non-const reference of type
'std::string&' from a temporary of type 'const char*'

Where line 20 is the bit that says: Note("hello world\n");

Why would I need "const" when I pass by reference, but not need const when
I pass by value?




> Should I put the "&" in front of msg? i.e.
>
> void _say(const string &msg){
>
>
>> Almost perfect. I would make a few minor changes.
>>
>> void _say(const string msg&){
>> 	cout<<msg;
>> }
>>
>>
>> void Note(const string msg&){
>> 	_say("Note: "+msg);
>> }
>>
>> Minor efficiencies. In your code in when note() is called the string is
>> copied so msg is a copy of the input. In _say("Note: "+msg);
>>  you are creating a new string, but that string is also copied. Setting
>> up
>> a call by reference saves 2 copies in this case. The compiler can
>> optimize the _say function to where the call by reference does not
>> matter, but not the note() function which is external.
>>
>>
>> --
>> Jerry Feldman <gaf at blu.org>
>> Boston Linux and Unix
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>>
>>
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>
>
> --
>
>
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