1 files changed, 9 insertions, 0 deletions
diff --git a/lexer.py b/lexer.py
index 913a9aa..11e02f1 100644
--- a/lexer.py
+++ b/lexer.py
@@ -125,6 +125,15 @@ def lex(inp, tokens):
         return lex(inp[1:], tokens)
     # numbers
     elif nxt in list(DIGITS) or nxt in ("+", "-", "."):
+        # + and - are symbols, too
+        if nxt in ("+", "-"):
+            after = peek(inp[1:])
+            if after not in DIGITS: # parse a symbol
+                token, remainder = lex_symbol(inp)
+                if peek(remainder) not in (None, CLOSE_PAREN, " "):
+                    raise Exception("spaces required between tokens")
+                tokens.append(token)
+                return lex(remainder, tokens)
         token, remainder = lex_number(inp)
         tokens.append(token)
         return lex(remainder, tokens)