Matrix initialization, with a powerful "dim(x,y)", ref to: http://stackoverflow.com/questions/14294780/how-to-pass-a-method-but-not-activate-it-in-io-language

gistfile1.io

List2D := Object clone
List2D dim := method(x, y,
	target := list()
	fillStrategy := "const"
	
	default := call evalArgAt(2)
	if(default type == "Block", fillStrategy := "func")

	for(i, 1, y, 
		subTarget := list()
		for(j, 1, x,
			subTarget append( 
				if(fillStrategy == "const", 
					default,
					default call(i,j)) ))
		target append(subTarget))
	target)

List2D dim(3,2) println
List2D dim(3,2,"foo") println
List2D dim(2,3, block(a,b, if((a+b) % 2 == 0, "foo", "bar"))) println

the fillStrategy here is actually not necessary to be compared every time when filling elements.