S-expressions: Difference between revisions
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Or, parsing by hand (rather than with a parser combinator library) and printing a parse tree diagram: |
Or, parsing by hand (rather than with a parser combinator library) and printing a parse tree diagram: |
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<lang haskell> |
<lang haskell>{-# LANGUAGE TupleSections #-} |
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import Data.Bifunctor (bimap) |
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import Data.List.Split (splitOn) |
import Data.List.Split (splitOn) |
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import Data.Maybe (catMaybes, fromMaybe, listToMaybe) |
import Data.Maybe (catMaybes, fromMaybe, listToMaybe) |
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------------------------ DATA TYPE ----------------------- |
------------------------ DATA TYPE ----------------------- |
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data Val |
data Val |
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= Int Integer |
= Int Integer |
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parseExpr = go |
parseExpr = go |
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where |
where |
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go |
go = until finished parseToken . ([],) |
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finished (_, []) = True |
finished (_, []) = True |
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atom [] = List [] |
atom [] = List [] |
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atom s@('"' : _) = |
atom s@('"' : _) = |
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fromMaybe |
fromMaybe |
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(List []) |
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(maybeRead ("String " <> s)) |
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atom s = |
atom s = |
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headDef ( |
headDef (Symbol s) $ |
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catMaybes $ |
catMaybes $ |
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maybeRead |
maybeRead |
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<$> |
<$> fmap (<> (' ' : s)) ["Int", "Float"] |
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<> ["Symbol \"" <> s <> "\""] |
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) |
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| ⚫ | |||
| ⚫ | |||
| ⚫ | |||
maybeRead :: String -> Maybe Val |
maybeRead :: String -> Maybe Val |
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spacedBrackets (c : cs) |
spacedBrackets (c : cs) |
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| c `elem` "()" = ' ' : c : " " <> spacedBrackets cs |
| c `elem` "()" = ' ' : c : " " <> spacedBrackets cs |
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| otherwise = c : spacedBrackets cs |
| otherwise = c : spacedBrackets cs |
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------------------------- GENERIC ------------------------ |
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| ⚫ | |||
| ⚫ | |||
| ⚫ | |||
{{Out}} |
{{Out}} |
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<pre>Symbol "List" |
<pre>Symbol "List" |
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