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Idiom #193 Transpose a two-dimensional matrix

Declare two two-dimensional arrays a and b of dimension n*m and m*n, respectively. Assign to b the transpose of a (i.e. the value with index interchange).

(def a [[1 2 3] [4 5 6] [7 8 9]])
(def b (apply (partial mapv vector) a))
real :: a(n,m), b(m,n)

b = transpose(a)
const a = [[1, 2, 3], [4, 5, 6]]
const m = a[0].length
const b = Array.from({ length: m }, (_, n) => a.map(row => row[n]))
local a = {}

for x = 1, n do
  local t = {}
  for y = 1, m do
    t[y] = {x, y}
  end
  a[x] = t
end
  
local b = {}

for y = 1, m do
  local t = {}
  for x = 1, n do
    t[x] = a[x][y]
  end
  b[y] = t
end
uses typ, omv;
var
  A: array[1..m, 1..n] of ArbFloat;
  B: array[1..n, 1..m] of ArbFloat;
begin
  ... some code to fill A
  omvtrm(
    A[1,1], m, n, n,
    B[1,1], m
  );
end.
use PDL::Basic qw(sequence transpose);
my ($m, $n) = (3, 2);
my $A = sequence $m, $n;
my $B = transpose $A;
a = [[1,2], [3,4], [5,6]]
b = list(map(list, zip(*a)))
import numpy as np
a = np.array([[1,2], [3,4], [5,6]])
b = a.T
a = [[1,2], [3,4], [5,6]]
b = a.transpose

New implementation...
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tkoenig