Data commit

Task/Playing-cards/Jq/playing-cards.jq

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+# Uncomment for gojq:
+# def _nwise($n):
+#  def nw: if length <= $n then . else .[0:$n] , (.[$n:] | nw) end;
+#  nw;
+
+# Output: a prn in range(0;$n) where $n is .
+def prn:
+  if . == 1 then 0
+  else . as $n
+  | (($n-1)|tostring|length) as $w
+  | [limit($w; inputs)] | join("") | tonumber
+  | if . < $n then . else ($n | prn) end
+  end;
+
+def knuthShuffle:
+  length as $n
+  | if $n <= 1 then .
+    else {i: $n, a: .}
+    | until(.i ==  0;
+        .i += -1
+        | (.i + 1 | prn) as $j
+        | .a[.i] as $t
+        | .a[.i] = .a[$j]
+        | .a[$j] = $t)
+    | .a
+    end;
+
+def Pip: ["A", "2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K"];
+
+def Suit: ["♦", "♣", "♥", "♠"];
+
+def Card(pip; suit): pip + suit;
+
+def Deck: Card(Pip[]; Suit[]);
+
+# Deal one round of the cards in .deck to the players
+# represented by .hands,
+# but if there are not enough cards, do nothing except add .error to the input
+# Input {deck, hands}
+def deal:
+  (.hands | length) as $nplayers
+  | if $nplayers > (.deck|length) then .error = "not enough cards"
+    else reduce range(0;$nplayers) as $i (.; .hands[$i] += [.deck[$i]])
+    | .deck |= .[$nplayers:]
+
+# Deal $n cards to $nplayers players if there are enough cards in the input deck
+# Input: a deck
+# Output: {deck, hands}
+def deal($n; $nplayers):
+  if $n * $nplayers > length then "deal/2: not enough cards" | error
+  else {deck: ., hands: [range(0; $nplayers)|[]]}
+  | until( .hands[0]|length == $n; deal)
+  end ;
+
+# display an entire deck or else just the cards
+def display:
+  if length == 52 then _nwise(13) | join(" ")
+  else join(" ")
+  end;
+
+def task:
+  Deck
+  | "After creation, the deck consists of:", display, "",
+    (knuthShuffle
+     | "After shuffling:", display, "",
+       ( deal(5; 4)
+         | "After dealing 5 cards each to 4 players, the hands are:",
+         (.hands[] | display), "", "... leaving \(.deck|length)  cards") ) ;
+
+task