Thread: g++ complains while msvc doesn't

Am I using the conditional operator in a wrong way?

Based on my knowledge, you are.

The usual pattern is:

Code:

variable = condition ? true_option : false_option;

Where both true_option and false_option have to be expressions or value-returning functions that can be assigned to variable. I don't know what your code is supposed to do, so I can't rewrite your example. Maybe explain your intent.

Regarding switch(bool), it's probably because switch actually takes an integer argument. I think using if-else looks neater, any reason not to use that?

Hmm, I'm surprised it works on MSVC but maybe I have a gap in my knowledge there. With that being said, I don't see why...

Code:

if(pointInNumber)
    scCTX.SetState(SCE_DD_DEFAULT);

...doesn't suffice on its own.

Edit: Just tested it myself and it seems you cannot have incompatible types in each conditional expression (if SetState() returned bool, it would work). Usually GCC is right in these cases though, so I recommend you investigate the rules behind this and adapt your code, if necessary.

Actually I was writing a Scintilla lexer, and that code is supposed to check if there are multiple decimal points in a number in which case the "number" is no longer considered a number and hence not styled.

EDIT (after noticing your edit): Got it. Thanks for your help!

?: has higher precedence than =

So what you've written is this
( pointInNumber ? scCTX.SetState(SCE_DD_DEFAULT) : pointInNumber ) = true;

Since the error message complains about void, then it seems obvious that you can't do scCTX.SetState(SCE_DD_DEFAULT) = true, hence the use of the ?: is wrong.

FWIW, the use of ?: in place of the more obvious if / then / else construct was a mistake in itself.

The conditional operator is fine if you're doing

Code:

if (a)
    var = true_expr;
else
    var = false_expr;

This just amounts to var = a ? true_expr : false_expr;

What you're trying to do is an abuse of the operator. It is means for the above construct and only that.