How to Call function with default parameter? [duplicate]

Question

I have a function define in header file as this:

int myfunction(VpTR*& viewporttable,  wchar* vpname=L"*Active", OpenMode f=fR);

how i can call this function but ignore second argument? I tried calling it with the following code but an error message appeared: expected an expression

myfunction(myviewporttable,, fR);

can i omit this argument but it still understands L "* Active" as the called value?

You can't. C++ doesn't have named parameters support some other languages have so you cannot omit any parameter — UnholySheep
– UnholySheep, Commented Sep 25, 2020 at 14:10
You can still call it with arguments: myfunction(myviewportable, L"*Active", fR) — Adrian Maire
– Adrian Maire, Commented Sep 25, 2020 at 14:12
Make a helper forwarding function int myfunction(VpTR*& viewporttable, OpenMode f) { return myfunction(viewporttable, L"*Active", f); } — Eljay
– Eljay, Commented Sep 25, 2020 at 14:13

πάντα ῥεῖ · Accepted Answer · 2020-09-25 14:14:48Z

0

The syntax doesn't allow to omit parameter values at arbitrary positions, only those at the very end of the list.

You have to overload 2 versions:

int myfunction(VpTR*& viewporttable,  OpenMode f=fR) {
    return myfunction(viewporttable,L"*Active",L"*Active",f);
}

int myfunction(VpTR*& viewporttable,  wchar* vpname=L"*Active", OpenMode f=fR);

Then you can call

myfunction(myviewporttable, fR);

answered Sep 25, 2020 at 14:14

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