diff options
| -rw-r--r-- | macros.lisp | 34 |
1 files changed, 23 insertions, 11 deletions
diff --git a/macros.lisp b/macros.lisp index d560b68..9ecf7ef 100644 --- a/macros.lisp +++ b/macros.lisp @@ -174,28 +174,40 @@ printed. But the next time only the return value is used. -(defmacro monadic> ((init &key (fail-when #'null) fail-with) &rest functions) +(defmacro monadic ((&key (exit-when #'null) (exit-with #'identity)) init &rest functions) "A threading macro. Some examples: -(monadic> - (\"hey dude what's the big idea\") ; starting state +(monadic () + \"hey dude what's the big idea\" ; starting state #$(values (search \"the\" $s) $s) ; multiple-values are passed along as arguments #$(subseq $2 $1)) : returns the result of the last form should return \"the big idea\" -(monadic> - (\"hey dude what's the big idea?\" :fail-with \"☹\") +(monadic (:exit-with \"☹\") + \"hey dude what's the big idea?\" #$(values (search \"NOOOOOOPE\" $s) $s) #$(subseq $2 $1)) should return \"☹\". -FAIL-WHEN should be a function, a predicate, that operates on the -first value returned from one of the forms. If non-NIL, the MONADIC> -form returns with the value of the expression FAIL-WITH . +EXIT-WHEN should be a function, a predicate, that operates on the +first value returned from one of the forms. If non-NIL, the MONADIC +form returns by calling the EXIT-WITH function on the list of values +returned the the most recently called function. -The default value of FAIL-WHEN is the predicate NULL. +e.g + +(monadic (:exit-when #'evenp + :exit-with #$(list* :failed $x)) + 33 + #$(+ 11 $x) + #$(- 5 $x)) + +will return (:FAILED 44) + +The default value of EXIT-WHEN is the predicate NULL. +The default value of EXIT-WITH is IDENTITY " (let ((vals (gensym)) @@ -205,8 +217,8 @@ The default value of FAIL-WHEN is the predicate NULL. (block ,block-label (dolist (,fn (list ,@functions) (values-list ,vals)) (setq ,vals (multiple-value-list (apply ,fn ,vals))) - (when (funcall ,fail-when (car ,vals)) - (return-from ,block-label ,fail-with))))))) + (when (funcall ,exit-when (car ,vals)) + (return-from ,block-label (funcall ,exit-with ,vals)))))))) |