Function frontOr

If value is valid, it returns the internal value. This means .front for a range, .get for a Nullable!T, etc. If value is invalid, then elseValue is returned. If an elsePred is provided than that is called.

auto frontOr(alias elsePred, T) (
  auto ref T value
);

auto frontOr(T, U) (
  auto ref T value,
  lazy U elseValue
);

elsePred can return void as well, in which case frontOr also returns void.

Parameters

NameDescription
value the value to check
elseValue the value to get if value is invalid
elsePred the perdicate to call if value is invalid

Returns

  • Nullable!T: value.get or elseValue
  • Optional!T: value.front or elseValue
  • Range!T: value.front or elseValue

    • Example

    import optional.optional: some, no;

auto opt0 = no!int;
auto opt1 = some(1);

// Get or optional
assert(opt0.frontOr(789) == 789);
assert(opt1.frontOr(789) == 1);

// Lambdas
() @nogc {
    assert(opt0.frontOr!(() => 789) == 789);
    assert(opt1.frontOr!(() => 789) == 1);
}();

// Same with arrays/ranges

int[] arr0;
int[] arr1  = [1, 2];

// Get frontOr optional
assert(arr0.frontOr(789) == 789);
assert(arr1.frontOr(789) == 1);

// Lambdas
() @nogc {
    assert(arr0.frontOr!(() => 789) == 789);
    assert(arr1.frontOr!(() => 789) == 1);
}();