From 3e21ae3fa660b188bc20caec8c96c1f678405c25 Mon Sep 17 00:00:00 2001
From: Mark Wooding <mdw@distorted.org.uk>
Date: Sun, 10 Jan 2016 13:51:04 +0000
Subject: [PATCH] src/final.lisp: Add convenient macro for testing parsers at
 the REPL.

Nothing especially awesome.
---
 doc/SYMBOLS    |  1 +
 doc/misc.tex   |  5 +++++
 src/final.lisp | 25 +++++++++++++++++++++++++
 3 files changed, 31 insertions(+)

diff --git a/doc/SYMBOLS b/doc/SYMBOLS
index d9587ee..59df763 100644
--- a/doc/SYMBOLS
+++ b/doc/SYMBOLS
@@ -408,6 +408,7 @@ final.lisp
   *sod-version*                                 variable
   exercise                                      function
   test-module                                   function
+  test-parser                                   macro
 
 fragment-parse.lisp
   parse-delimited-fragment                      function
diff --git a/doc/misc.tex b/doc/misc.tex
index 8c8b9c1..06791f4 100644
--- a/doc/misc.tex
+++ b/doc/misc.tex
@@ -533,6 +533,11 @@ These symbols are defined in the @!optparse| package.
 \begin{describe}{fun}{test-module @<path> @<reason>}
 \end{describe}
 
+\begin{describe}{mac}
+    {test-parser (@<scanner>) @<parser> @<input>
+      @> @<success-flag> @<result> @<remainder>}
+\end{describe}
+
 \begin{describe}{fun}{exercise}
 \end{describe}
 
diff --git a/src/final.lisp b/src/final.lisp
index 7d4468e..071ebc9 100644
--- 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.
 
-- 
2.11.0