stehau

W2/calculator/Calculator.fsx

@@ -0,0 +1,27 @@
+open System.Text
+open FSharp.Text.Lexing
+open FSharp.Text.Parsing
+
+(* Both lex and parse a program. *)
+let parse (s : string) =
+    Parser.Prog Lexer.Token
+    <| LexBuffer<_>.FromBytes (Encoding.UTF8.GetBytes s)
+
+(* Continually evaluate user expressions. *)
+let loop () =
+    let mutable running = true
+    while running do
+        printf "Input an expression: "
+        try
+            let program = System.Console.ReadLine()
+            if program = "exit"
+            then
+                running <- false
+            else
+                printfn "Parse result: %A" (parse program)
+        with
+        | Failure msg -> printfn "%s" msg
+        | :? System.ArgumentNullException ->
+            running <- false
+
+loop ()