diff options
| -rw-r--r-- | hofs.lisp | 23 | ||||
| -rw-r--r-- | macros.lisp | 13 | ||||
| -rw-r--r-- | package.lisp | 5 |
3 files changed, 35 insertions, 6 deletions
diff --git a/hofs.lisp b/hofs.lisp new file mode 100644 index 0000000..7eb1d51 --- /dev/null +++ b/hofs.lisp @@ -0,0 +1,23 @@ +;;; hofs.lisp -- higher-order functions + +(in-package :lambda-riffs) + +(defun labmda-if (pred then &optional (else (constantly nil))) + "Returns a function that applies PRED and conditionally executes +THEN when PRED returned non-nil or otherwise executes ELSE. Each of +PRED, THEN, and ELSE are assumed to accept the same arguments." + (lambda (&rest args) + (if (apply pred args) + (apply then args) + (apply else args)))) + +(defun lambda-cond (&rest pairs) + "PAIRS is a list: PRED1 F1 PRED2 F2 ... + Returns a function that applies FN to the argumetns for the first N + such that PREDN returns non-nil. Each of the PREDN and FN are + assumed to accept the same arguments." + (lambda (&rest args) + (loop for (pred fn . more) on pairs by #'cddr + when (apply pred args) + return (apply fn args)))) + diff --git a/macros.lisp b/macros.lisp index fa93bc5..8cf528f 100644 --- a/macros.lisp +++ b/macros.lisp @@ -23,8 +23,7 @@ (declare (ignore subchar infix)) (let ((form1 (read stream))) (if (symbolp form1) - (list '$ (list (concatenate 'string "$" - (symbol-name form1))) + (list '$ (list (concatenate 'string "$" (symbol-name form1))) (read stream)) (list '$ () form1)))))) @@ -110,7 +109,11 @@ surrounding form. `(lambda ,new-params ,expr))) - - - +(defmacro closure (&body body) + "Creates a lambda that accepts any number of arguments, all of which + are ignored." + (let ((args (gensym))) + `(lambda (&rest ,args) + (declare (ignorable ,args)) + ,@body))) diff --git a/package.lisp b/package.lisp index dcadede..2db36f3 100644 --- a/package.lisp +++ b/package.lisp @@ -1,4 +1,7 @@ ;;;; package.lisp (defpackage #:lambda-riffs - (:use #:cl)) + (:use #:cl) + (:export #:closure + #:lambda-if + #:lambda-cond)) |