Tree datastructures: Difference between revisions
→{{header|Haskell}}: Added a less instructive variant, using the pre-cooked Data.Tree
(→{{header|Haskell}}: added solution) |
(→{{header|Haskell}}: Added a less instructive variant, using the pre-cooked Data.Tree) |
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λ> ttest == from (from ttest :: Indent String)
True</pre>
And less instructively – just relying a little passively on the existing Data.Tree,
we might also write something like:
<lang haskell>import Data.Bifunctor (bimap, first)
import Data.Char (isSpace)
import Data.List (find)
import Data.Tree (Forest, Tree (..), drawTree)
-------- MAPPINGS BETWEEN INDENTED LINES AND TREES -------
forestFromNestLevels :: [(Int, a)] -> Forest a
forestFromNestLevels = go
where
go [] = []
go ((n, v) : xs) =
uncurry (:) $
bimap (Node v . go) go (span ((n <) . fst) xs)
indentLevelsFromLines :: [String] -> [(Int, String)]
indentLevelsFromLines xs =
let pairs = first length . span isSpace <$> xs
indentUnit = maybe 1 fst (find ((0 <) . fst) pairs)
in first (`div` indentUnit) <$> pairs
outlineFromForest ::
(String -> a -> String) ->
String ->
Forest a ->
String
outlineFromForest showRoot tabString forest =
let go indent node =
showRoot indent (rootLabel node) :
(subForest node >>= go ((<>) tabString indent))
in unlines $ forest >>= go ""
-------------------------- TESTS -------------------------
main :: IO ()
main = do
putStrLn "Trees from indented text:\n"
let trees =
forestFromNestLevels $
indentLevelsFromLines test
putStrLn $ drawTree $ Node "" trees
putStrLn "Indented text from trees:\n"
putStrLn $ outlineFromForest (<>) " " trees
test :: [String]
test =
[ "RosettaCode",
" rocks",
" code",
" comparison",
" wiki",
" mocks",
" trolling",
"Some lists",
" may",
" be",
" irregular"
]</lang>
{{Out}}
<pre>Trees from indented text:
|
+- RosettaCode
| |
| +- rocks
| | |
| | +- code
| | |
| | +- comparison
| | |
| | `- wiki
| |
| `- mocks
| |
| `- trolling
|
`- Some lists
|
+- may
|
+- be
|
`- irregular
Indented text from trees:
RosettaCode
rocks
code
comparison
wiki
mocks
trolling
Some lists
may
be
irregular</pre>
=={{header|Julia}}==
| |||