
Yes, you're right. It wrote it in pseudoVMCode, as it is not clear whether a and b are the first, second, ... local variable. But if we assume, that a = local 0 and b = local 1, as well as x = 4 and y = 3, the code would change to:
// push b[3] to the top of the stack
push local 1
push constant 3
add
pop pointer 1
push that 0
// write the stack's top value to a[4]
push local 0
push constant 4
add
pop pointer 1
pop that 0
The question remains the same, doesn't it?
