src/final.lisp: Add convenient macro for testing parsers at the REPL.

[sod] / src / final.lisp

diff --git a/src/final.lisp b/src/final.lisp
index 7d4468e..071ebc9 100644 (file)
--- a/src/final.lisp
+++ b/src/final.lisp
@@ -50,6 +50,31 @@
                   :if-does-not-exist :create)
     (output-module (read-module path) reason out)))
 
+(export 'test-parser)
+(defmacro test-parser ((scanner &key) parser input)
+  "Convenient macro for testing parsers at the REPL.
+
+   This is a macro so that the parser can use the fancy syntax.  The name
+   SCANNER is bound to a `sod-token-scanner' reading tokens from the INPUT
+   string.  Then the PARSER is invoked and three values are returned: a
+   `successp' flag indicating whether the parser succeeded; the result,
+   output or error indicator, of the parser; and a list consisting of the
+   lookahead token type and value, and a string containing the untokenized
+   remaining input."
+  (once-only (input)
+    (with-gensyms (char-scanner value winp consumedp where)
+      `(let* ((,char-scanner (make-string-scanner ,input))
+             (,scanner (make-instance 'sod-token-scanner
+                                      :char-scanner ,char-scanner
+                                      :filename "<test-input>")))
+        (with-parser-context (token-scanner-context :scanner ,scanner)
+          (multiple-value-bind (,value ,winp ,consumedp) (parse ,parser)
+            (declare (ignore ,consumedp))
+            (let ((,where (scanner-capture-place ,char-scanner)))
+              (values ,winp ,value
+                      (list (token-type ,scanner) (token-value ,scanner)
+                            (subseq ,input ,where))))))))))
+
 ;;;--------------------------------------------------------------------------
 ;;; Calisthenics.