Part 3

Multidimensional Arrays

Given:

a←1 2 1 ⋄ b←2 3 4 1 ⋄ c←1 5 3 4 1 5

What is the output of the following?

1. +/⍳99
2. ⍴⍬
3. ⍴⍬,⍬
4. ⋄ ⍳3 ⋄⋄⍳5
5. ⍴⍪⍪⍳2
6. 3⍪⍪⍳2
7. ⍴,⍪⍳8
8. ⎕←⍴a,b
9. ⍴,b∘.+c
10. ⍴⎕
11. ⍴⍪7

Selecting from Arrays

Given

 a←1 2 1 ⋄ b←2 3 4 1 ⋄ c←1 5 3 4 1 5
 A←'abcdefghij' ⋄ B←6⌊c∘.+c ⋄ C←b∘.×B

what are the results of the following expressions?

1. ⍴B
2. ⍴C
3. ⍴A[a]
4. ⍴A[B]
5. ⍴A[3]
6. ⍴A[3 10]
7. ⍴A[c,c]
8. ⍴A[12⍴1]
9. ⍴B[a;a]
10. ⍴B[a;c]
11. ⍴B[1;b]
12. ⍴B[B;2]
13. ⍴B[,2;b]
14. ⍴B[B;B]
15. b[b]
16. ⍴88[a]
17. 2 2↑B
18. 2 2↓B
19. 2 2 3↑C
20. 0 2 8↑C
21. 0 2 8↑B
22. 2/a
23. 0 1 2/a
24. ⍴b/b
25. ⍴b/[1]C
26. ⍴c/B
27. ⍴c/C
28. ⍴c⌿C
29. ⍴a/B
30. ⍴⎕←a⌷C
31. ⍴C[a;a;a]
32. ⍴a a a⌷C
33. ⍴C[a;a;]
34. ⍴C[a;;]
35. ⍴C[;;]
36. ⍴B[;]
37. ⍴A[]
38. ⍴12[]
39. 2 8 ↑ B
40. 0 9 ↑ B
41. 3 1 ↑ 2 2↓B
42. 3 ↑ 2 2↓B
43. B[;1] ←⍳9