My Crafttweaker script

import crafttweaker.item.IItemStack;

val backpackMaterialMap as IItemStack[int] = {
    0 : <minecraft:dye:0>,
    1 : <minecraft:gunpowder>,
    2 : <minecraft:grass>,
	4 : <minecraft:dirt>,
	5 : <minecraft:dirt>,
	6 : <minecraft:dirt>,
	7 : <minecraft:dirt>,
	8 : <minecraft:dirt>,
	9 : <minecraft:dirt>,
	10 : <minecraft:dirt>,
	11 : <minecraft:dirt>,
	12 : <minecraft:dirt>,
	13 : <minecraft:dirt>,
	14 : <minecraft:dirt>,
	15 : <minecraft:dirt>
};


for i in 0 to 16 {
    print(backpackMaterialMap[i].displayName);
}