Make a list and remove the odd values?

Questions
1

Right now, I’ve been trying
threshold[min_,max_]=Apply[Select[EvenQ],Range[min,max]

However, that’s not working. It seems extremely difficult to create a list and change it in one go.

2

There are many ways to do this you can try:

Clear[threshold];
threshold[min_, max_] := DeleteCases[Range[min, max], _?OddQ]
3

Well I am not very smart, see my photo, but that is interesting. I know it is a shot list and I guess zero is even so being very discrete . . .

In[3]:= n := 0

In[6]:= Case[{n, n + 1}, n]

Out[6]= Case[{0, 1}, 0]

wait . . .

In[3]:= n := 0

In[7]:= Case[{n, n + 1}, n + 1]

Out[7]= Case[{0, 1}, 1]
4

why did this work, or in other words, what does this tell the interpreter to do that was different from how I typed it? Why was “:=” better than “=”? and what is “_?”? Thanks for the answer!

5

Apply replaces the Head of an expression. Changing the Head to Select[EvenQ] results in this Select[EvenQ][1, 2, 3, 4, 5] which is invalid. You need this

threshold[min_, max_] := Range[min, max] // Select[EvenQ]