Add support for JSLT (#1129)

[1] https://github.com/schibsted/jslt

languages.json

@@ -767,6 +767,12 @@
       "quotes": [["\\\"", "\\\""]],
       "extensions": ["jq"]
     },
+    "JSLT": {
+      "name": "JSLT",
+      "line_comment": ["//"],
+      "quotes": [["\\\"", "\\\""]],
+      "extensions": ["jslt"]
+    },
     "Json": {
       "name": "JSON",
       "blank": true,

tests/data/jslt.jslt

@@ -0,0 +1,126 @@
+// 126 lines 80 code 20 comments 26 blanks
+
+// https://github.com/schibsted/jslt/blob/master/examples/queens.jslt
+// ===========================================================================
+//  N-Queens problem solution in JSLT
+
+// board is n lists of length n
+//  0 => no queen
+//  1 => queen
+
+// queens(8) produces
+// [
+//   [ 1, 0, 0, 0, 0, 0, 0, 0 ],
+//   [ 0, 0, 0, 0, 1, 0, 0, 0 ],
+//   [ 0, 0, 0, 0, 0, 0, 0, 1 ],
+//   [ 0, 0, 0, 0, 0, 1, 0, 0 ],
+//   [ 0, 0, 1, 0, 0, 0, 0, 0 ],
+//   [ 0, 0, 0, 0, 0, 0, 1, 0 ],
+//   [ 0, 1, 0, 0, 0, 0, 0, 0 ],
+//   [ 0, 0, 0, 1, 0, 0, 0, 0 ]
+// ]
+
+def queens(n)
+  solve(0, make-board($n))
+
+def range(length, list)
+  if (size($list) < $length)
+    range($length, $list + [size($list)])
+  else
+    $list
+
+def zeroes(length)
+  [for (range($length, [])) 0]
+
+def make-board(n)
+  [for (range($n, [])) zeroes($n)]
+
+def solve(row, board)
+  let n = size($board)
+  if ($row == $n)
+    $board
+  else
+    let tries = [for (range($n, []))
+      let newboard = place-queen($row, ., $board)
+      if (is-ok($newboard))
+        solve($row + 1, $newboard)
+      else
+        null]
+
+    filter($tries)[0]
+
+def is-ok(board)
+  rows-ok($board) and cols-ok($board) and diagonals-ok($board)
+
+def rows-ok(board)
+  all-ok([for ($board) sum(.) <= 1])
+
+def cols-ok(board)
+  // 0, 1, 2, 3, ...
+  let indexes = range(size($board), [])
+
+  // list of columns instead of list of rows
+  let columns = [for ($indexes)
+    let col = (.)
+    [for ($board) .[$col]]
+  ]
+
+  rows-ok($columns)
+
+def diagonals-ok(board)
+  let n = size($board)
+  let offsets = range($n - 1, [])[1 : ] // starts with 1
+
+  let diagonals-right = (
+    [diagonal-right($board, 0, 0)] +
+    [for ($offsets) diagonal-right($board, 0, .)] +
+    [for ($offsets) diagonal-right($board, ., 0)]
+  )
+
+  let diagonals-left = (
+    [diagonal-left($board, 0, $n - 1)] +
+    [for ($offsets) diagonal-left($board, ., $n - 1)] +
+    [for ($offsets) diagonal-left($board, 0, .)]
+  )
+
+  rows-ok($diagonals-right + $diagonals-left)
+
+def diagonal-right(board, rowoff, coloff)
+  if ($rowoff >= size($board) or $coloff >= size($board))
+    []
+  else
+    [$board[$rowoff][$coloff]] + diagonal-right($board, $rowoff+1, $coloff+1)
+
+def diagonal-left(board, rowoff, coloff)
+  if ($rowoff >= size($board) or $coloff < 0)
+    []
+  else
+    diagonal-left($board, $rowoff + 1, $coloff - 1) + [$board[$rowoff][$coloff]]
+
+def sum(numbers)
+  if (not($numbers))
+    0
+  else
+    $numbers[0] + sum($numbers[1 : ])
+
+def all-ok(booleans)
+  if (not($booleans))
+    true
+  else
+    $booleans[0] and all-ok($booleans[1 : ])
+
+def place-queen(row, col, board)
+  let changerow = $board[$row]
+  let newrow = $changerow[ : $col] + [1] + $changerow[$col + 1 : ]
+
+  $board[ : $row] + [$newrow] + $board[$row + 1 : ]
+
+def filter(array)
+  if (not($array))
+    []
+  else if ($array[0])
+    [$array[0]] + filter($array[1 : ])
+  else
+    filter($array[1 : ])
+
+queens(8)