define-expression-macro

Define a macro for Coalton expression context.

define-expression-macro defines a macro that expands into Coalton expression syntax.

Syntax

(define-expression-macro name lambda-list
  body ...)

Semantics

It has the same expansion model as cl:defmacro.
The macro body runs as Common Lisp and returns Coalton source forms.
The macro is intended for use where a Coalton expression is expected.
Coalton-aware REPLs may use this role to evaluate bare calls as Coalton expressions.

Example

(define-expression-macro if-some ((name expr) then else)
  `(match ,expr
     ((Some ,name) ,then)
     ((None) ,else)))

(coalton
  (if-some (x maybe-count)
    (+ x 1)
    0))