Add lexing for negative integers

1 files changed, 6 insertions, 1 deletions

diff --git a/DSL.hs b/DSL.hs
index 3244c7f..ea4c8c2 100644
--- a/DSL.hs
+++ b/DSL.hs
@@ -82,7 +82,12 @@ wsL :: DSLLexer
 wsL = buildDSLLexer (mult1 $ satisfy isSpace) (const T_WHITESPACE)
 
 intLiteralL :: DSLLexer
-intLiteralL = buildDSLLexer (mult1 $ satisfy isDigit) (T_INT_LITERAL . read)
+intLiteralL = buildDSLLexer go (T_INT_LITERAL . read)
+  where
+    go = do
+      sign   <- optional $ token '-'
+      digits <- mult1 $ satisfy isDigit
+      result $ maybe digits (:digits) sign
 
 mainLexer :: Parser Char [DSLToken]
 mainLexer = phrase $ mult1 $ firstOf subLexers