Question

Write a condition in the given blank below using comparison operator to get the require output from this code. ​​​​​​​​​

fun Filter(P,nil) = nil

|​Filter(P,x::xs) = if P(x) then x::Filter(P,xs) else Filter(P,xs) ;

Filter( fn x => ____________________________, [1,10,23,8,5,16,3]);

output:

val it = [1,8,5,3] : int list

Answer 1

The list it shows that the numbers generated are [1, 8, 5, 3] which can be interpreted in several ways such as it represents a list of numbers which are less than 10 or which are 1-digit numbers so for our condition which we can implement to get it, it represents a list of numbers such that if the number is x, then if x<10 then we should get it in the list or else we shouldn't. Hence, the condition should be.

Filter( fn x => if x<10 then x else (), [1,10,23,8,5,16,3]);