Overview of Lambdas¶

A lambda begins with -<. It may declare captures, parameters, a return type, and either an expression or block body.

Expression bodies¶

VAR source I32 := 4;

VAR implicit_capture AUTO := -< = source;
VAR reference_capture AUTO := -< [source] = source;
VAR value_capture AUTO := -< [=source] = source;
VAR no_capture AUTO := -< [] :I32 = 7;

The = introduces the lambda's returned expression; it is not assignment.

Block bodies and parameters¶

VAR limit_to_max AUTO := -< (@value I32, @maximum I32): I32
{
  IF (value > maximum)
  {
    RETURN maximum;
  }
  RETURN value;
};

ASSERT(limit_to_max(@value 7, @maximum 5) == 5);

Lambda parameters use the same named and positional syntax as functions. Named parameters are preferred for ordinary lambda interfaces; positional parameters remain available when position is intentional. A return type is optional when it can be deduced from the body.

Capture lists¶

Omitting a capture list permits implicit reference capture.
[name] explicitly captures name by reference.
[=name] captures name by value.
[] rejects any use of an uncaptured enclosing runtime local.

Capture discovery follows statically reachable paths. A name used only inside a discarded STATIC_IF branch does not force an invalid capture.

Lambdas are function values and can be passed through AUTO(name) parameters. See Procedure pointers and function values.

Reference¶

See the Lambdas Reference for the complete language rules, constraints, and technical edge cases.