transpose.js 1.3 KB

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  1. import _curry1 from "./internal/_curry1.js";
  2. /**
  3. * Transposes the rows and columns of a 2D list.
  4. * When passed a list of `n` lists of length `x`,
  5. * returns a list of `x` lists of length `n`.
  6. *
  7. *
  8. * @func
  9. * @memberOf R
  10. * @since v0.19.0
  11. * @category List
  12. * @sig [[a]] -> [[a]]
  13. * @param {Array} list A 2D list
  14. * @return {Array} A 2D list
  15. * @example
  16. *
  17. * R.transpose([[1, 'a'], [2, 'b'], [3, 'c']]) //=> [[1, 2, 3], ['a', 'b', 'c']]
  18. * R.transpose([[1, 2, 3], ['a', 'b', 'c']]) //=> [[1, 'a'], [2, 'b'], [3, 'c']]
  19. *
  20. * // If some of the rows are shorter than the following rows, their elements are skipped:
  21. * R.transpose([[10, 11], [20], [], [30, 31, 32]]) //=> [[10, 20, 30], [11, 31], [32]]
  22. * @symb R.transpose([[a], [b], [c]]) = [a, b, c]
  23. * @symb R.transpose([[a, b], [c, d]]) = [[a, c], [b, d]]
  24. * @symb R.transpose([[a, b], [c]]) = [[a, c], [b]]
  25. */
  26. var transpose =
  27. /*#__PURE__*/
  28. _curry1(function transpose(outerlist) {
  29. var i = 0;
  30. var result = [];
  31. while (i < outerlist.length) {
  32. var innerlist = outerlist[i];
  33. var j = 0;
  34. while (j < innerlist.length) {
  35. if (typeof result[j] === 'undefined') {
  36. result[j] = [];
  37. }
  38. result[j].push(innerlist[j]);
  39. j += 1;
  40. }
  41. i += 1;
  42. }
  43. return result;
  44. });
  45. export default transpose;