Method `%()

Method `%

mixed `%(object arg1, mixed arg2)
mixed `%(mixed arg1, object arg2)
string `%(string arg1, int arg2)
array `%(array arg1, int arg2)
float `%(float arg1, float|int arg2)
float `%(int arg1, float arg2)
int `%(int arg1, int arg2)

Description

Modulo.

Every expression with the % operator becomes a call to this function, i.e. a%b is the same as predef::`%(a,b).

Returns

If arg1 is an object that implements lfun::`%() then that function will be called with arg2 as the single argument.

If arg2 is an object that implements lfun::``%() then that function will be called with arg2 as the single argument.

Otherwise the result will be as follows:

arg1 can have any of the following types:

string|array	If arg2 is positive, the result will be the last `%(sizeof(arg1), arg2) elements of arg1. If arg2 is negative, the result will be the first `%(sizeof(arg1), -arg2) elements of arg1.
int|float	The result will be arg1 - arg2*floor(arg1/arg2). The result will be a float if either arg1 or arg2 is a float, and an int otherwise.

For numbers, this means that

1. a % b always has the same sign as b (typically b is positive; array size, rsa modulo, etc, and a varies a lot more than b).

2. The function f(x) = x % n behaves in a sane way; as x increases, f(x) cycles through the values 0,1, ..., n-1, 0, .... Nothing strange happens when you cross zero.

3. The % operator implements the binary "mod" operation, as defined by Donald Knuth (see the Art of Computer Programming, 1.2.4). It should be noted that Pike treats %-by-0 as an error rather than returning 0, though.

4. / and % are compatible, so that a == b*floor(a/b) + a%b for all a and b.

See also

`/, floor()