Source code in the clu programming language

% Represents one playing card.
card = cluster is make, parse, unparse, equal, all_cards
    rep = struct[pip: int, suit: char]
    own suits: string := "CHSD";
    own pips: sequence[string] := sequence[string]$
        ["A","2","3","4","5","6","7","8","9","10","J","Q","K"]
       
    find_pip = proc (pip: string) returns (int) signals (bad_format)
        for i: int in int$from_to(1, sequence[string]$size(pips)) do
            if pips[i] = pip then return(i) end
        end
        signal bad_format
    end find_pip
    
    make = proc (pip: int, suit: char) returns (cvt) signals (bad_format)
        if string$indexc(suit, suits) = 0
           cor ~(pip >= 1 cand pip <= 13) 
            then signal bad_format
        end
        return(rep${pip: pip, suit: suit})
    end make
    
    parse = proc (s: string) returns (cvt) signals (bad_format)
        size: int := string$size(s)
        if size<2 cor size>3 then signal bad_format end
        pip: string := string$substr(s, 1, size-1)
        suit: char := string$rest(s, size-1)[1]
        return(down(make(find_pip(pip), suit))) resignal bad_format
    end parse
    
    unparse = proc (c: cvt) returns (string)
        return( pips[c.pip] || string$c2s(c.suit) )
    end unparse
    
    equal = proc (a, b: cvt) returns (bool)
        return( a.pip = b.pip cand a.suit = b.suit )
    end equal
    
    % Yield all cards in the canonical order
    all_cards = iter () yields (cvt)
        for suit: char in string$chars(suits) do
            for pip: int in int$from_to(1,sequence[string]$size(pips)) do 
                yield(down(make(pip, suit)))
             end
        end
    end all_cards
end card

% Represents a deck
deck = cluster is new, shuffle, cards, deal, unparse
    rep = array[card]
    
    new = proc () returns (cvt)
        d: rep := rep$new()
        for c: card in card$all_cards() do rep$addh(d, c) end
        return(d)
    end new
    
    shuffle = proc (d: cvt)
        lo: int := rep$low(d)
        hi: int := rep$high(d)
        for i: int in int$from_to_by(hi, lo+1, -1) do
            j: int := lo + random$next(i-lo)
            c: card := d[i]
            d[i] := d[j]
            d[j] := c
        end
    end shuffle
    
    cards = iter (d: cvt) yields (card)
        for c: card in rep$elements(d) do yield(c) end
    end cards
    
    deal = proc (d: cvt) returns (card) signals (empty)
        if rep$empty(d) then signal empty end
        return(rep$reml(d))
    end deal
    
    unparse = proc (d: cvt) returns (string)
        ss: stream := stream$create_output()
        n: int := 0
        for c: card in cards(up(d)) do
            if n~=0 cand n//13=0 then stream$putc(ss, '\n')
            elseif n~=0 then stream$putc(ss, ' ')
            end
            stream$puts(ss, card$unparse(c))
            n := n+1
        end
        return(stream$get_contents(ss))
    end unparse
end deck

start_up = proc ()
    po: stream := stream$primary_output()
    % seed the RNG
    d_: date := now()
    random$seed(d_.second + 60*(d_.minute + 60*d_.hour))
    
    % make a new deck
    d: deck := deck$new()
    stream$putl(po, "New deck: ")
    stream$putl(po, deck$unparse(d))
    
    % shuffle the deck
    deck$shuffle(d)
    stream$putl(po, "\nShuffled deck: ")
    stream$putl(po, deck$unparse(d))
    
    % deal some cards
    stream$puts(po, "\nDealing 10 cards:")
    for i: int in int$from_to(1, 10) do
        stream$puts(po, " " || card$unparse(deck$deal(d)))
    end
    
    % show remaining deck
    stream$putl(po, "\n\nRemaining cards in deck:")
    stream$putl(po, deck$unparse(d))
end start_up