FindNumbers←{
⍝ ⍺: An integer x and real number y
⍝ ⍵: Numeric array
⍝ ←: All numbers with digits made by
⍝    concatenating elements in ⍵,
⍝    which have exactly x digits
⍝    and a value less than y
     (x y)←⍺
     l←¯1+x              ⍝ Power of 10 with x digits
     c←,∘.,⍨⍵            ⍝ All possible concatenations of ⍵
     n←10∘⊥¨c            ⍝ In base 10
     n⌿⍨((10*l)>n)≠n<y   ⍝ ←
 }