Dyalog APL, sort rows in a matrix

Question

I would like to sort numbers within each row of a matrix, for example, 3 3 rho 2 3 1 4 5 7 1 9 8 should become 3 3 rho 1 2 3 4 5 7 1 8 9.

I am new to Dyalog APL, and know how to generate, via grade the matrix 3 3 rho 3 2 1 1 2 3 1 3 2 from the initial matrix.

Answer 1

I would like to sort numbers …

There is actually no sort primitive in APL (allegedly, Dyalog APL 19 is supposed to get one). Until then, you would use one of the monadic Grade functions (Grade Up ⍋ in this case), which returns an array of its argument's indices (starting at ⎕IO) permuted such that they can be used as ordered references back into the original array. Provide them (enclosed, and in a fork) to the dyadic Index function ⌷ to reference the items in the original array: ⊂⍤⍒⌷⊢. The enclosing (with the monadic Enclose function ⊂) is necessary because when using the Index function ⌷, references to multiple items conveyed as a plain array of indices would instead be interpreted as a single reference into a multi-dimensional array along a number of axes.

… within each row of a matrix

Use the dyadic Rank operator ⍤ to apply the monadic sort function defined above successively to the first-level (1) sub-arrays of the matrix: ⍤1

      ((⊂⍤⍋⌷⊢)⍤1) 3 3 ⍴ 2 3 1 4 5 7 1 9 8
1 2 3
4 5 7
1 8 9