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Template std.functional.partial

Partially applies fun by tying its first argument to arg.

template partial(alias fun, alias arg) ;

Contained Functions

NameDescription
partial

Parameters

NameDescription
fun A callable
arg The first argument to apply to fun

Returns

A new function which calls fun with arg plus the passed parameters.

Example

int fun(int a, int b) { return a + b; }
alias fun5 = partial!(fun, 5);
writeln(fun5(6)); // 11
// Note that in most cases you'd use an alias instead of a value
// assignment. Using an alias allows you to partially evaluate template
// functions without committing to a particular type of the function.

Example

// Overloads are resolved when the partially applied function is called
// with the remaining arguments.
struct S
{
    static char fun(int i, string s) { return s[i]; }
    static int fun(int a, int b) { return a * b; }
}
alias fun3 = partial!(S.fun, 3);
writeln(fun3("hello")); // 'l'
writeln(fun3(10)); // 30

Authors

Andrei Alexandrescu

License

Boost License 1.0.