Very simple question with MemberQ

Questions
1

I want to make a function that will take list A, match it with list B, and delete any non-matching elements in list A.

I imagine that this will be very easy to accomplish using MemberQ, however, I cannot think up a way.

Help,

2

Hi,

Try the following:

fun[A_List, B_List] := Select[A, ! MemberQ[B, #] &];
fun[{a, b, c, d}, {c, d, e, f}]

Out[]= {a, b}

Youngjoo Chung

3

Depending on the exact usage and how repeated elements should be treated, functions like Complement and DeleteCases might also be helpful. Take a look at this thread for some interesting examples.

4

Thank you, however a quick question.

Which variable is the pure fuction taking as #?

5

The pure function

!MemberQ[B, #] &

is applied to each element (#) of A. In the above example, it will be a, b, c, d.

6

Maybe this SE post can help.