列出对数组有条件的理解？

Question

I have an array that contains tuples that look like this: [((Int, Int), Int)] . I am trying to create a new array with list comprehensions that says to only add all 3 Ints if the 3rd Int == a certain number. I have it written as

newArray = [((x,y),z) | ((x,y),z)<-oldArray, (snd oldArray) == 5]

However, when I try to run the code that contains this, it says "couldn't match expected type" and point the error at my conditional. "Couldn't match expected type '(a0, Int)' with actual type '[((Int, Int), Int)]'" .

Answer 1

oldArray is a list, always and forever, even inside the comprehension, so snd can't be applied to it. Use z == 5 instead.