Operator overloading with templates [duplicate]

Question

Im trying to run a program with templates using operator < ,> methods, im getting a compiler error telling me "instantiated from here" and cannot convert Temps<double>' todouble' in return ,,The problem starts when i call the operator function Heres the code..

 template <class T> class Temps { private: T a; public: Temps() { } Temps(T b) { a=b; } T operator<(Temps c) { if (a < c.a) { return *this; } return c; } T operator>(Temps c) { if (a > c.a) { return *this; } return c; } }; int main() { double d1 = -9.002515,d2=98.321,d3=1.024; Temps<double>mag(d1); Temps<double>lag(d3); Temps<double>tag; tag=mag < lag; system("pause"); return 0; }

I wouldn't use < to find the max. < should return bool. — Pubby
– Pubby, Commented Nov 18, 2011 at 0:55
That must be the weirdest semantics for a < operator I've ever seen. — Kerrek SB
– Kerrek SB, Commented Nov 18, 2011 at 1:26
Please don't do this. This kind of abuse of operator overloading is exactly the reason why operator overloading has such a bad reputation in some circles. Would it be so bad to have a max and a min unction for this instead of an operator which the casual reader of your code expects to do something completely different from what it does? — Grizzly
– Grizzly, Commented Nov 18, 2011 at 1:57

drdwilcox · Accepted Answer · 2011-11-18 03:41:28Z

Your < and > functions return a T, but you are trying to return a Temps<T>. What you probably want to return is either a or c.a. But the normal semantics of < and > is to return a bool, so you may want to return a < c.a for <:

bool operator <(Temps c) { return a < c.a; }

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