v1

14s shakespeare

Main.lean

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+def String.words (s : String) :=
+  s.split Char.isWhitespace |>.filter (¬·.isEmpty)
+def String.lines (s : String) :=
+  s.splitOn "\n" |>.filter (¬·.isEmpty)
+
+def List.unlines (xs : List String) : String
+  := xs.intersperse "\n" |> String.join
+
+def ex := "The heat bloomed\tin December\nas the carnival  season\n        kicked into gear.\nNearly helpless with sun and glare, I avoided Rio's brilliant\nsidewalks\n  and glittering beaches,\npanting in dark   corners\nand waiting out the inverted southern summer."
+
+#eval ex.words
+#eval ex.lines
+#eval IO.println ex.lines.unlines
+
+def sep : List a → List a → List a
+| a1::a1s, a2::a2s => a1::a2::sep a1s a2s
+| a1,       _      => a1
+
+def justify : Nat → List String → String
+| _,    [word] => word
+| width, words =>
+    let wordsLength   := List.sum (String.length <$> words)
+    let spacesNeeded  := width - wordsLength
+    let numSpaces     := words.length - 1
+    let smallSpaceLen := spacesNeeded / numSpaces
+    let smallSpace    := List.replicate smallSpaceLen ' '
+    let largeSpaces   := spacesNeeded % numSpaces
+    let smallSpaces   := numSpaces - largeSpaces
+    let largeSpace    := ' '::smallSpace
+    let spaces := List.replicate largeSpaces largeSpace
+               ++ List.replicate smallSpaces smallSpace
+               |>.map List.asString
+    String.join $ sep words spaces
+
+#eval justify 1 "Hello, world, how is it going?".words
+#eval justify 1 "Hello, world, how is it going?".words |>.length
+
+def breakUp (width : Nat) (words : List String) : List (List String) :=
+  let (_, line, lines) := words.foldl
+    (λ(left, line, lines) word ↦
+      if word.length < left
+      then (left - (word.length + 1), line++[word], lines)
+      else (width - word.length, [word], lines++[line]))
+    (width, [], [])
+  lines++[line]
+
+-- def breakUp (width : Nat) (words : List String)
+--   : List (List String) :=
+--   if width = 0 then [] else go width words [] []
+--   where
+--   go (left : Nat) (words line : List String) (lines : List $ List String) :=
+--   match left, words, line, lines with
+--   | _,    [],      l, ls => ls++[l]
+--   | left, (w::ws), l, ls =>
+--       if width < w.length
+--       then go width ws [w] ls
+--       else if left < w.length + 1
+--       then go width (w::ws) [] (ls++[l])
+--       else go (left - (w.length + 1)) ws (l++[w]) ls
+--   termination_by (left, words)
+
+
+def solve (width : Nat) :=
+  List.unlines ∘ List.map (justify width) ∘ breakUp width ∘ String.words
+
+#eval IO.println $ solve 40 ex
+
+def usage := "Usage: justify WIDTH"
+def fail : IO UInt32 := do IO.println usage; return 1
+
+def main : List String → IO UInt32
+| [width] =>
+  if let some width := width.toNat?
+  then do
+    let mut text := ""
+    let stdin ← IO.getStdin
+    while true do
+      let line ← stdin.getLine
+      if line.isEmpty then break
+      text := text ++ line
+    IO.println $ solve width text
+    return 0
+  else fail
+| _ => fail

README.md

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+# justify

lake-manifest.json

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+{"version": "1.1.0",
+ "packagesDir": ".lake/packages",
+ "packages": [],
+ "name": "justify",
+ "lakeDir": ".lake"}

lakefile.toml

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+name = "justify"
+version = "0.1.0"
+defaultTargets = ["justify"]
+
+[[lean_exe]]
+name = "justify"
+root = "Main"

lean-toolchain

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+leanprover/lean4:4.15.0