Method `-()

Method `-

mixed `-(mixed arg1)
mixed `-(mixed arg1, mixed arg2, mixed ... extras)
mixed `-(object arg1, mixed arg2)
mixed `-(mixed arg1, object arg2)
int `-(int arg1, int arg2)
float `-(float arg1, int|float arg2)
float `-(int|float arg1, float arg2)
string `-(string arg1, string arg2)
array `-(array arg1, array arg2)
mapping `-(mapping arg1, array arg2)
mapping `-(mapping arg1, mapping arg2)
mapping `-(mapping arg1, multiset arg2)
multiset `-(multiset arg1, multiset arg2)

Description

Negation/subtraction/set difference.

Every expression with the - operator becomes a call to this function, i.e. -a is the same as predef::`-(a) and a-b is the same as predef::`-(a,b). Longer - expressions are normally optimized to one call, so e.g. a-b-c becomes predef::`-(a,b,c).

Returns

If there's a single argument, that argument is returned negated. If arg1 is an object with an lfun::`-(), that function is called without arguments, and its result is returned.

If there are more than two arguments the result is: `-(`-(arg1, arg2), @extras).

Otherwise, if arg1 is an object with an lfun::`-(), that function is called with arg2 as argument, and its result is returned.

Otherwise, if arg2 is an object with an lfun::``-(), that function is called with arg1 as argument, and its result is returned.

Otherwise the result depends on the argument types:

arg1 can have any of the following types:

int|float	The result is arg1 - arg2, and is a float if either arg1 or arg2 is a float.
string	The result is arg1 with all nonoverlapping occurrences of the substring arg2 removed. In cases with two overlapping occurrences, the leftmost is removed.
array|mapping|multiset	The result is like arg1 but without the elements/indices that match any in arg2 (according to `>, `<, `== and, in the case of mappings, hash_value).

The function is not destructive on the arguments - the result is always a new instance.

Note

In Pike 7.0 and earlier the subtraction order was unspecified.

Note

If this operator is used with arrays or multisets containing objects which implement lfun::`==() but not lfun::`>() and lfun::`<(), the result will be undefined.

See also

`+()