Iterate through all combinations of values from ARBITRARY number of lists

[#1]

Can somebody suggest a solution to this.

I have multiple lists. I need to iterate through all possible combinations of values from these lists. The problem is that the number of lists I'm taking values from is decided at runtime. So I cannot write two nested 'for' loops for two lists and then three nested 'for' loops for three lists. I need somehow to pass\parse names of the lists (probably as a list itself) and then iterate through all of the lists\values in the lists.

Any ideas?

[#2]

I'm not sure how deep this can go before JMP thinks your recursion is too deep, so test first...If you have too many lists, there is a slightly less pretty work-around using a stack. But if each list has at least two elements, I think you'll run out of time first.

// the variable length list of variable length lists
L = {{"a", "b"}, {"c"}, {"d", "e", "f"}, {"g", "h", "i", "j"}};

result = {}; // a place to accumulate the results
p = {}; // a single result

// a recursive function to "nest the for loops"
generate = Function( {i}, // the "layer"
	{j}, // the local for-loop counter
	If( i > N Items( L ),
		result[N Items( result ) + 1] = p; // you could just use p at this point
		Return();
	);
	For( j = 1, j <= N Items( L[i] ), j += 1, // go through all the items at this layer
		Insert Into( p, L[i][j] ); // add each to the single result
		Recurse( i + 1 ); // go to next layer
		Remove From( p ); // remove from the single result
	);
);

generate( 1 ); // run the recursive function
Show( result );

result = {

{"a", "c", "d", "g"},

{"a", "c", "d", "h"},

{"a", "c", "d", "i"},

{"a", "c", "d", "j"},

{"a", "c", "e", "g"},

{"a", "c", "e", "h"},

{"a", "c", "e", "i"},

{"a", "c", "e", "j"},

{"a", "c", "f", "g"},

{"a", "c", "f", "h"},

{"a", "c", "f", "i"},

{"a", "c", "f", "j"},

{"b", "c", "d", "g"},

{"b", "c", "d", "h"},

{"b", "c", "d", "i"},

{"b", "c", "d", "j"},

{"b", "c", "e", "g"},

{"b", "c", "e", "h"},

{"b", "c", "e", "i"},

{"b", "c", "e", "j"},

{"b", "c", "f", "g"},

{"b", "c", "f", "h"},

{"b", "c", "f", "i"},

{"b", "c", "f", "j"}

};