Re: basic_string ctor

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"Stephen Howe" <stephenPOINThoweATtns-globalPOINTcom> wrote in message
news:%23gILBBHXFHA.160@xxxxxxxxxxxxxxxxxxxxxxx
>> The problem is
>>
>> void foo(std::string flarn) {
>> // anything at all
>> }
>>
>> With this type of function a char*
>> can be passed and std::string's ctor
>> will be called. You would have to
>> provide char* versions to use your
>> suggestion.
>
> Nonsense.
> This works for me on compiling with cl /GX /O1 nulltest.cpp:
> Your foo works without providing any char * versions.
>
>>>>>>>>>>>>>>>>>>
> #include <string>
> #include <iostream>
> using namespace std;
>
> void foo(std::string flarn)
> { cout << '[' << flarn << "]\n";
> }
>
> int main()
> {
> char *p = "Hello";
> char *q = "";
> char *r = 0;
>
> foo(p);
> foo(q);
> foo(r != 0 ? r : "");
>
> return 0;
> }

And the above can be easily codified with:

std::string empty_if_null( const char* p){ return p? p : ""; }

...

f( empty_if_null(r) );

Which is nicely self documenting in those cases where a null check is
needed, and is easy to find with an editor.

Jeff Flinn


.

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