Group 4
J symbol (left-brace): {
Monadic case:
Name: catalogue
Rank: 1 (vector) – applies to a vector y
Definition: { y returns all combinations of the elements in the boxes of y.
Please also include explanations for your answers to some of the following questions:
What is the catalogue of two boxed vectors (e.g., { 0 1;2 4 )?
What is the catalogue of three boxed strings (e.g., { 'bcs';'aeo';'dnt' )?
Dyadic case:
Name: from
Rank: 1 (left); _ (right) – applies to a vector on the left and the entire array on the right
Definition (numeric x): x { y returns the items of y at the positions specified by x. If x is positive, then positions are counted from the front of y. If x is negative, then the positions are counted from the back of y.
Definition (box x): x { y returns the sub-array of y indexed by position xi of axis i of y, where xi is the i-th element of x.
Please also include explanations for your answers to some of the following questions:
What is returned when x is positive?
What is returned when x is negative?
What is returned when x is zero?
What is returned when xi is greater than the length of the ith axis of y?
What is returned when x is a box?
What is returned when x is a list of boxes (e.g., (2 3;5 7) { i.10 10 )?