[Python-Dev] SyntaxError: can't assign to function call (original) (raw)

"Martin v. Löwis" martin at v.loewis.de
Fri Aug 11 21:48:43 CEST 2006

Neal Becker schrieb:

No. Array references (x[i]) and attribute references (x.a) represent "locations". Function calls represent values. This is no different than the distinction between lvalues and rvalues in C.

Except this syntax is valid in c++ where X() is a constructor call: X(whatever) += 2; is (or can be) valid c++

That's actually the less-interesting case. You would have to overload += to make it work, right?

The more interesting case is when X is a function that returns a reference:

int& X(int);

void foo(){ X(1) += 2; }

int bar, foobar; int& X(int t){ if(t) return bar; return foobar; }

Here, which variable gets incremented depends on whether the t argument is true; no overloading of assignment comes into play.

The trick is that C++ has functions that return lvalues; neither C nor Python has such things.

Regards, Martin

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