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Comments on Permutations of an array - APL
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Permutations of an array - APL
In Dyalog APL, there's a predefined function in the dfns library to generate a matrix of permutations for a list of the numbers from 1 to n.
I want to create the same functionality, except that it should work for any array, not just a range 1 to n, in APL NARS2000.
How do I implement that?
Post
I assume the built-in definition you're referring to is pmat. That illustrates how to solve your problem near the bottom. The idea is simply if σ is a permutation of length N and A is an array of length N, then A[σ] is A permuted by σ. This leads to a definition like:
permute←{⍵[pmat⊃⍴⍵]}
with
permute 'abc'
producing
abc
acb
bac
bca
cab
cba
(The example in the documentation uses {⍵[pmat⍴⍵]} but this seemed to lead to rank errors when I tried it in online interpreters using one of the definitions of pmat listed on that page.)
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