From: Samir Benmendil <me@rmz.io>
Date: Sun, 14 Jan 2018 00:19:18 +0000 (+0000)
Subject: Parse Atoms which start with a letter or symbol
X-Git-Url: https://git.rmz.io/my-scheme.git/commitdiff_plain/d06e8ae01efc00ea0eb6f0bed346032b004aca57?ds=sidebyside

Parse Atoms which start with a letter or symbol

`<|>` is a Parser combinator, the choice operator. It will try the first
parser, if it doesn't match anything, try the second parser, and so on.

`a:b` creates a list from `a` and `b`. Another possibility would be to
use `[a] ++ b`, where a new list with a single element is created `[a]`
and concatenated with `++`
---

diff --git a/app/Main.hs b/app/Main.hs
index 22de748..7c987ce 100644
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -22,6 +22,12 @@ parseString = do
     char '"'
     return $ String x
 
+parseAtom :: Parser LispVal
+parseAtom = do
+    a <- letter <|> symbol
+    b <- many (letter <|> digit <|> symbol)
+    return $ Atom (a:b)
+
 readExpr :: String -> String
 readExpr input = case parse (spaces >> symbol) "lisp" input of
     Left err -> "No match: " ++ show err