This is called operator overloading, and is done by implementing specific class methods. The compiler will recognize and use these methods when it compiles expressions involving the overloaded operators and the script class.
| op | opfunc |
| - | opNeg |
| ~ | opCom |
When the expression op a is compiled, the compiler will rewrite it as a.opfunc and compile that instead.
| op | opfunc |
| == | opEquals |
| != | opEquals |
| < | opCmp |
| <= | opCmp |
| > | opCmp |
| >= | opCmp |
The a == b expression will be rewritten as a.opEquals(b) and b.opEquals(a) and then the best match will be used. != is treated similarly, except that the result is negated. The opEquals method must be implemented to return a bool in order to be considered by the compiler.
The comparison operators are rewritten as a.opCmp(b) op 0 and 0 op b.opCmp(a) and then the best match is used. The opCmp method must be implemented to return a int in order to be considered by the compiler.
If an equality check is made and the opEquals method is not available the compiler looks for the opCmp method instead. So if the opCmp method is available it is really not necesary to implement the opEquals method, except for optimization reasons.
| op | opfunc |
| = | opAssign |
| += | opAddAssign |
| -= | opSubAssign |
| *= | opMulAssign |
| /= | opDivAssign |
| %= | opModAssign |
| &= | opAndAssign |
| |= | opOrAssign |
| ^= | opXorAssign |
| <<= | opShlAssign |
| >>= | opShrAssign |
| >>>= | opUShrAssign |
The assignment expressions a op b are rewritten as a.opfunc(b) and then the best matching method is used. An assignment operator can for example be implemented like this:
obj@ opAssign(const obj &in other)
{
// Do the proper assignment
...
// Return a handle to self, so that multiple assignments can be chained
return this;
}
All script classes have a default assignment operator that does a bitwise copy of the content of the class, so if that is all you want to do, then there is no need to implement this method.
| op | opfunc | opfunc_r |
| + | opAdd | opAdd_r |
| - | opSub | opSub_r |
| * | opMul | opMul_r |
| / | opDiv | opDiv_r |
| % | opMod | opMod_r |
| & | opAnd | opAnd_r |
| | | opOr | opOr_r |
| ^ | opXor | opXor_r |
| << | opShl | opShl_r |
| >> | opShr | opShr_r |
| >>> | opUShr | opUShr_r |
The expressions with binary operators a op b will be rewritten as a.opfunc(b) and b.opfunc_r(a) and then the best match will be used.
1.5.9