Initial data commit

Task/Arithmetic-evaluation/F-Sharp/arithmetic-evaluation-2.fs

@@ -0,0 +1,24 @@
+{
+module Lexer
+
+open Parser  // we need the terminal tokens from the Parser
+
+let lexeme = Lexing.LexBuffer<_>.LexemeString
+}
+
+let intNum     = '-'? ['0'-'9']+
+let whitespace = ' ' | '\t'
+let newline    = '\n' | '\r' '\n'
+
+rule token = parse
+    | intNum     { INT (lexeme lexbuf |> int) }
+    | '+'        { PLUS }
+    | '-'        { MINUS }
+    | '*'        { TIMES }
+    | '/'        { DIVIDE }
+    | '('        { LPAREN }
+    | ')'        { RPAREN }
+    | whitespace { token lexbuf }
+    | newline    { lexbuf.EndPos <- lexbuf.EndPos.NextLine; token lexbuf }
+    | eof        { EOF }
+    | _          { failwithf "unrecognized input: '%s'" <| lexeme lexbuf }