Andrei Alexandrescu wrote:
KennyTM~ wrote:
On Dec 1, 09 22:30, Steven Schveighoffer wrote:
An idea I just had when thinking about how ugly opDispatch and opBinary
operators will be if we get those was, wouldn't it be cool if the
compiler could translate:
myTemplateMethod("abc" || "def")() if(condition) {}
to
myTemplateMethod(string __x)() if((__x == "abc" || __x == "def") &&
condition) {}
It makes dispatch based on compile-time strings much more palatable, for
example:
opDispatch("foo" || "bar")() {...}
opBinary("+" || "-" || "*")(int rhs) {...}
instead of:
opDispatch(string fn)() if(fn == "foo" || fn == "bar") {...}
opBinary(string op)() if(op == "+" || op == "-" || op == "*")(int rhs)
{...}
In fact, it can be generalized to any type which has literals:
factorial(int x)(){ return factorial!(x-1)() * x;}
factorial(1)() { return 1;}
What I don't know is if the || works in all cases -- because something
like true || false is a valid expression. Maybe someone can come up with
a better way.
-Steve
Alternative suggestion:
Make "x in y" returns a bool and works for arrays. Then you can write
int opBinary(string s)(int rhs) if (s in ["+", "-", "*", "/", "^",
"|", "&"]) { ... }
It's a bit difficult to see a very thin operator mask a linear
operation, but I'm thinking maybe "x in y" could be defined if y is a
compile-time array. In that case, the compiler knows the operation and
the operand so it may decide to change representation as it finds fit.
Andrei
What do you suggest using when you need to find out if an object is in
an array? Arrays lacking opIn bothers me.
