This is the first of a series of posts as I go through Project Euler in APL to stretch my knowledge of APL. I hope to post one problem a day to this blog.

Problem #1:

∇R←PEONE;X;⎕IO
 ⎕IO←1

 ⍝ Find the sum of all the multiples of 3 or 5 below 1000.
 X←⍳999
 R←+/((0=3∣X)∨0=5∣X)/X
∇