// http://groups.google.com/group/comp.lang.functional/browse_thread/thread/4eaaa738cd11e484/6cf90f2035485515#6cf90f2035485515

I:{x@&x _lin y}         / intersect
U:?,                    / union
C:{(!_ x^y)_dvl z}      / complement

/ index from element pattern
ie:{x _sv+(,/,/:\:)/(),/:@[y;&y=-1;:[;!x]]}

/ element patterns from sequence pattern
es:{{@[x;z;:;y]}[x#-1;y _dv -1]'+:[1=#m:(n#x)_vs!c:_ x^n:+/y>-1;m;m[;&*>':m]]}

/ cartesian product without indices
cp:{+(y#x)_vs(!_ x^y)_dvl z}

/ e:es[4;-1 2 -1]
/ i:?,/ie[4]'e
/ q:cp[3;4;i]
/ r:cp[3;4;()]

cp0:{[c;n;p]+(n#c)_vs(!_ c^n)_dvl,/{c _sv+(,/,/:\:)/(),/:@[x;&x=-1;:[;!c]]}'p}

cp0[2;3;,0 -1 1]
cp[2;3;?,/ie[3]'es[3;0 -1 1]]

\

cp0[2;3;(0 -1 1;1 -1 0)]
cp0[2;3;(0 -1 1;1 -1 1)]
cp0[3;2;,2 -1]

\

-1 2 -1 card 4

2 -1 -1 -1
-1 2 -1 -1
-1 -1 2 -1
-1 -1 -1 2

-1 2 -1 3 card 6

generate card#-1
generate consecutive indices for non -1s
populate over





\

cp:{[c;n;p]+(n#c)_vs(!_ c^n)_dvl,/{c _sv+(,/,/:\:)/(),/:@[x;&x=-1;:[;!c]]}'p}

cp[2;3;,0 -1 1]
cp[2;3;(0 -1 1;1 -1 0)]
cp[2;3;(0 -1 1;1 -1 1)]
cp[3;2;,2 -1]

\

now, for some golf ...

things get simpler if we replace the wildcard symbol (in this
implementation, -1) with values from the set.  e.g.,

cp[2;3;,(0;0 1;1)]

then:

  cp:{[c;n;p]+(n#c)_vs(!_ c^n)_dvl,/(c _sv+(,/,/:\:)/(),/:)'p}

  cp[2;3;,(0;0 1;1)]
(0 0 0
 0 1 0
 1 0 0
 1 0 1
 1 1 0
 1 1 1)

shorter still if we let cp's argument-names default:

  cp:{+(y#x)_vs(!_ x^y)_dvl,/(x _sv+(,/,/:\:)/(),/:)'z}

moreover, the initial + (transpose) is for display purposes only, so:

  cp:{(y#x)_vs(!_ x^y)_dvl,/(x _sv+(,/,/:\:)/(),/:)'z}

  cp[2;3;,(0;0 1;1)]
(0 0 1 1 1 1
 0 1 0 0 1 1
 0 0 0 1 0 1)