Add (and test) sub, add, inc/decrement, and bit-complement to lexer

1 files changed, 19 insertions, 2 deletions

diff --git a/src/modules/lexer/lexer.scm b/src/modules/lexer/lexer.scm
index a6be215..4078db4 100644
--- a/src/modules/lexer/lexer.scm
+++ b/src/modules/lexer/lexer.scm
@@ -28,13 +28,25 @@ current input port."
        'close-brace)
       ((eqv? chr #\;)
        'semi-colon)
+      ((eqv? chr #\~)
+       'complement)
 
-      ((char-alphabetic? chr)
-       (lookup-keyword (read-identifier chr)))
+      ((eqv? chr #\+)
+       (if (take-two? chr)
+           'increment
+           'add))
+
+      ((eqv? chr #\-)
+       (if (take-two? chr)
+           'decrement
+           'sub))
 
       ((char-numeric? chr)
        (read-constant chr))
 
+      ((char-alphabetic? chr)
+       (lookup-keyword (read-identifier chr)))
+
       (#t (error "illegal lexical syntax")))))
 
 (define (read-constant chr)
@@ -58,6 +70,11 @@ current input port."
             (#t (reverse chrs-so-far)))))
   (list->string (read-identifier-helper (list chr))))
 
+(define (take-two? chr)
+  (if (eqv? chr (peek-char))
+      (read-char)
+      #f))
+
 (define (lookup-keyword id)
   "Given identifier ID, converts it to a keyword
 if one is known."