S-expressions: Difference between revisions
m
→{{header|Haskell}}
Line 3,030:
Or, parsing by hand (rather than with a parser combinator library) and printing a parse tree diagram:
<lang haskell>
import Data.Bifunctor (bimap)
import Data.List.Split (splitOn)
import Data.Maybe (catMaybes, fromMaybe, listToMaybe)
Line 3,036 ⟶ 3,038:
------------------------ DATA TYPE -----------------------
data Val
= Int Integer
Line 3,063 ⟶ 3,064:
parseExpr = go
where
go
finished (_, []) = True
Line 3,082 ⟶ 3,083:
atom [] = List []
atom s@('"' : _) =
fromMaybe
(List [])
(maybeRead ("String " <> s))
atom s =
headDef (
catMaybes $
maybeRead
<$>
headDef :: a -> [a] -> a▼
headDef d [] = d▼
headDef _ (x : _) = x▼
maybeRead :: String -> Maybe Val
Line 3,119 ⟶ 3,116:
spacedBrackets (c : cs)
| c `elem` "()" = ' ' : c : " " <> spacedBrackets cs
| otherwise = c : spacedBrackets cs
------------------------- GENERIC ------------------------
▲headDef :: a -> [a] -> a
▲headDef d [] = d
▲headDef _ (x : _) = x</lang>
{{Out}}
<pre>Symbol "List"
| |||