From: Samir Benmendil <me@rmz.io>
Date: Tue, 23 Jan 2018 22:27:16 +0000 (+0000)
Subject: Show values (except Lists)
X-Git-Url: https://git.rmz.io/my-scheme.git/commitdiff_plain/fabc3d8bdaef310b2f18bc53735ad7ee53518822?ds=inline

Show values (except Lists)

We introduce a `showVal :: LispVal -> String` function, to turn a
LispVal into a printable string.

This function uses pattern matching to "specialize" on various types.
The declaration that matches the specific type is chosen.
---

diff --git a/app/Main.hs b/app/Main.hs
index fb8294a..1495605 100644
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -94,7 +94,15 @@ parseExpr = parseString
 readExpr :: String -> String
 readExpr input = case parse parseExpr "lisp" input of
     Left err -> "No match: " ++ show err
-    Right val -> "Found value: " ++ show val
+    Right val -> "Found value: " ++ showVal val
+
+showVal :: LispVal -> String
+showVal (Atom atom)   = atom
+showVal (Number n)    = show n
+showVal (String str)  = "\"" ++ str ++ "\""
+showVal (Character c) = "'" ++ [c] ++ "'"
+showVal (Bool True)   = "#t"
+showVal (Bool False)  = "#f"
 
 main :: IO ()
 main = do