A first, rough lexer for elisp still missing some stuff.

* module/language/elisp/lexer.scm: New lexer file.
* test-suite/Makefile.am: Register elisp-reader.test as new test.
* test-suite/tests/elisp-reader.test: New test-case.

module/language/elisp/lexer.scm

@@ -0,0 +1,162 @@
+;;; Guile Emac Lisp
+
+;; Copyright (C) 2001 Free Software Foundation, Inc.
+
+;; This program is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation; either version 2, or (at your option)
+;; any later version.
+;; 
+;; This program 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 General Public License for more details.
+;; 
+;; You should have received a copy of the GNU General Public License
+;; along with this program; see the file COPYING.  If not, write to
+;; the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+;; Boston, MA 02111-1307, USA.
+
+;;; Code:
+
+(define-module (language elisp lexer)
+  #:use-module (ice-9 regex)
+  #:export (get-lexer))
+
+; This is the lexical analyzer for the elisp reader.  It is hand-written
+; instead of using some generator because I think that's most viable in this
+; case and easy enough.
+
+
+; Read a symbol or number from a port until something follows that marks the
+; start of a new token (like whitespace or parentheses).  The data read is
+; returned as a string for further conversion to the correct type, but we also
+; return what this is (integer/float/symbol).
+; If any escaped character is found, it must be a symbol.  Otherwise we
+; at the end check the result-string against regular expressions to determine
+; if it is possibly an integer or a float.
+
+(define integer-regex (make-regexp "^[+-]?[0-9]+\\.?$"))
+(define float-regex
+  (make-regexp "^[+-]?([0-9]+\\.?[0-9]*|[0-9]*\\.?[0-9]+)(e[+-]?[0-9]+)?$"))
+
+; A dot is also allowed literally, only a single dort alone is parsed as the
+; 'dot' terminal for dotted lists.
+(define no-escape-punctuation (string->char-set "-+=*/_~!@$%^&:<>{}?."))
+
+(define (get-symbol-or-number port)
+  (let iterate ((result-chars '())
+                (had-escape #f))
+    (let* ((c (read-char port))
+           (finish (lambda ()
+                     (let ((result (list->string (reverse result-chars))))
+                       (values
+                         (cond
+                           ((and (not had-escape)
+                                 (regexp-exec integer-regex result))
+                            'integer)
+                           ((and (not had-escape)
+                                 (regexp-exec float-regex result))
+                            'float)
+                           (else 'symbol))
+                         result))))
+           (need-no-escape? (lambda (c)
+                              (or (char-numeric? c)
+                                  (char-alphabetic? c)
+                                  (char-set-contains? no-escape-punctuation
+                                                      c)))))
+      (cond
+        ((eof-object? c) (finish))
+        ((need-no-escape? c) (iterate (cons c result-chars) had-escape))
+        ((char=? c #\\) (iterate (cons (read-char port) result-chars) #t))
+        (else
+          (unread-char c port)
+          (finish))))))
+  
+
+; Main lexer routine, which is given a port and does look for the next token.
+
+(define (lex port)
+  (let ((return (let ((file (if (file-port? port) (port-filename port) #f))
+                      (line (1+ (port-line port)))
+                      (column (1+ (port-column port))))
+                  (lambda (token value)
+                    (let ((obj (cons token value)))
+                      (set-source-property! obj 'filename file)
+                      (set-source-property! obj 'line line)
+                      (set-source-property! obj 'column column)
+                      obj))))
+        ; Read afterwards so the source-properties are correct above
+        ; and actually point to the very character to be read.
+        (c (read-char port)))
+    (cond
+
+      ; End of input must be specially marked to the parser.
+      ((eof-object? c) '*eoi*)
+
+      ; Whitespace, just skip it.
+      ((char-whitespace? c) (lex port))
+
+      ; The dot is only the one for dotted lists if followed by
+      ; whitespace.  Otherwise it is considered part of a number of symbol.
+      ((and (char=? c #\.)
+            (char-whitespace? (peek-char port)))
+       (return 'dot #f))
+
+
+      ; Continue checking for literal character values.
+      (else
+        (case c
+
+          ; A line comment, skip until end-of-line is found.
+          ((#\;)
+           (let iterate ()
+             (let ((cur (read-char port)))
+               (if (or (eof-object? cur) (char=? cur #\newline))
+                 (lex port)
+                 (iterate)))))
+
+          ; Parentheses and other special-meaning single characters.
+          ((#\() (return 'paren-open #f))
+          ((#\)) (return 'paren-close #f))
+          ((#\[) (return 'square-open #f))
+          ((#\]) (return 'square-close #f))
+          ((#\') (return 'quote #f))
+          ((#\`) (return 'backquote #f))
+          ((#\,) (return 'unquote #f))
+
+          ; Remaining are numbers and symbols.  Process input until next
+          ; whitespace is found, and see if it looks like a number
+          ; (float/integer) or symbol and return accordingly.
+          (else
+            (unread-char c port)
+            (call-with-values
+              (lambda ()
+                (get-symbol-or-number port))
+              (lambda (type str)
+                (case type
+                  ((symbol) (return 'symbol (string->symbol str)))
+                  ((integer)
+                   ; In elisp, something like "1." is an integer, while
+                   ; string->number returns an inexact real.  Thus we
+                   ; need a conversion here, but it should always result in
+                   ; an integer!
+                   (return 'integer
+                           (let ((num (inexact->exact (string->number str))))
+                             (if (not (integer? num))
+                               (error "Expected integer" str num))
+                             num)))
+                  ((float)
+                   (return 'float (let ((num (string->number str)))
+                                    (if (exact? num)
+                                      (error "Expected inexact float" str num))
+                                    num)))
+                  (else (error "Wrong number/symbol type" type)))))))))))
+
+
+; Build a lexer thunk for a port.  This is the exported routine which can be
+; used to create a lexer for the parser to use.
+
+(define (get-lexer port)
+  (lambda ()
+    (lex port)))

test-suite/Makefile.am

@@ -33,6 +33,7 @@ SCM_TESTS = tests/alist.test			\
 	    tests/continuations.test		\
 	    tests/elisp.test			\
 	    tests/elisp-compiler.text		\
+	    tests/elisp-reader.text		\
 	    tests/environments.test		\
 	    tests/eval.test			\
 	    tests/exceptions.test		\

test-suite/tests/elisp-reader.test

@@ -0,0 +1,87 @@
+;;;; elisp-reader.test --- Test the reader used by the Elisp compiler.
+;;;;
+;;;; Copyright (C) 2009 Free Software Foundation, Inc.
+;;;; Daniel Kraft
+;;;;
+;;;; 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 3 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+
+(define-module (test-elisp-reader)
+  :use-module (test-suite lib)
+  :use-module (language elisp lexer))
+
+
+; ==============================================================================
+; Test the lexer.
+
+; This is of course somewhat redundant with the full parser checks, but probably
+; can't hurt and is useful in developing the lexer itself.
+
+(define (get-string-lexer str)
+  (call-with-input-string str get-lexer))
+
+(define (lex-string str)
+  (let ((lexer (get-string-lexer str)))
+    (let iterate ((result '()))
+      (let ((token (lexer)))
+        (if (eq? token '*eoi*)
+          (reverse result)
+          (iterate (cons token result)))))))
+
+(with-test-prefix "Lexer"
+
+  (let ((lexer (get-string-lexer "")))
+    (pass-if "end-of-input"
+      (and (eq? (lexer) '*eoi*)
+           (eq? (lexer) '*eoi*)
+           (eq? (lexer) '*eoi*))))
+
+  (pass-if "single character tokens"
+    (equal? (lex-string "()[]'`, . ")
+      '((paren-open . #f) (paren-close . #f)
+        (square-open . #f) (square-close . #f)
+        (quote . #f) (backquote . #f) (unquote . #f) (dot . #f))))
+
+  (pass-if "whitespace and comments"
+    (equal? (lex-string "   (\n\t) ; this is a comment\n.   ; until eof")
+      '((paren-open . #f) (paren-close . #f) (dot . #f))))
+
+  (pass-if "source properties"
+    (let ((x (car (lex-string "\n\n  \n  .  \n"))))
+      (and (= (source-property x 'line) 4)
+           (= (source-property x 'column) 3))))
+
+  (pass-if "symbols"
+    (equal? (lex-string "foo FOO char-to-string 1+ \\+1
+                         \\(*\\ 1\\ 2\\)
+                         +-*/_~!@$%^&=:<>{}
+                         abc(def)ghi .e5")
+            `((symbol . foo) (symbol . FOO) (symbol . char-to-string)
+              (symbol . 1+) (symbol . ,(string->symbol "+1"))
+              (symbol . ,(string->symbol "(* 1 2)"))
+              (symbol . +-*/_~!@$%^&=:<>{})
+              (symbol . abc) (paren-open . #f) (symbol . def)
+              (paren-close . #f) (symbol . ghi) (symbol . .e5))))
+
+  ; Here we make use of the property that exact/inexact numbers are not equal?
+  ; even when they have the same numeric value!
+  (pass-if "integers"
+    (equal? (lex-string "-1 1 1. +1 01234")
+            '((integer . -1) (integer . 1) (integer . 1) (integer . 1)
+              (integer . 1234))))
+  (pass-if "floats"
+    (equal? (lex-string "1500.0 15e2 15.e2 1.5e3 .15e4 -.345e-2")
+            '((float . 1500.0) (float . 1500.0) (float . 1500.0)
+              (float . 1500.0) (float . 1500.0)
+              (float . -0.00345)))))