;;; PLT Scheme Inference Collection ;;; facts.ss ;;; Copyright (c) 2006 M. Douglas Williams ;;; ;;; This library is free software; you can redistribute it and/or ;;; modify it under the terms of the GNU Lesser General Public ;;; License as published by the Free Software Foundation; either ;;; version 2.1 of the License, or (at your option) any later version. ;;; ;;; This library is distributed in the hope that it will be useful, ;;; but WITHOUT ANY WARRANTY; without even the implied warranty of ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU ;;; Lesser General Public License for more details. ;;; ;;; You should have received a copy of the GNU Lesser General Public ;;; License along with this library; if not, write to the Free ;;; Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA ;;; 02111-1307 USA. ;;; (module facts mzscheme (provide (all-defined)) ;; fact?: any -> boolean (define (fact? x) (or (and (pair? x) (symbol? (car x))) (and (vector? x) (> (vector-length x) 0) (symbol? (vector-ref x 0))))) ;; fact-first: fact? -> symbol (define (fact-first fact) (cond ((pair? fact) (car fact)) ((vector? fact) (vector-ref fact 0)) ((struct? fact) (vector-ref (struct->vector fact) 0)))) )