moves-in-squared-strings-ii

Moves in squared strings (II)

You are given a string of n lines, each substring being n characters long: For example:

s = "abcd\nefgh\nijkl\nmnop"

We will study some transformations of this square of strings.

• Clock rotation 180 degrees: rot

rot(s) => "ponm\nlkji\nhgfe\ndcba"

• selfie_and_rot(s) (or selfieAndRot or selfie-and-rot) It is initial string + string obtained by clock rotation 180 degrees with dots interspersed in order (hopefully) to better show the rotation when printed.

s = "abcd\nefgh\nijkl\nmnop" --> 
"abcd....\nefgh....\nijkl....\nmnop....\n....ponm\n....lkji\n....hgfe\n....dcba"

or printed:

|rotation        |selfie_and_rot
|abcd --> ponm   |abcd --> abcd....
|efgh     lkji   |efgh     efgh....
|ijkl     hgfe   |ijkl     ijkl....   
|mnop     dcba   |mnop     mnop....
                           ....ponm
                           ....lkji
                           ....hgfe
                           ....dcba

Task

• Write these two functions rotand selfie_and_rot

and

• high-order function oper(fct, s) where

• fct is the function of one variable f to apply to the string s (fct will be one of rot, selfie_and_rot)

Example

s = "abcd\nefgh\nijkl\nmnop"
oper(rot, s) => "ponm\nlkji\nhgfe\ndcba"
oper(selfie_and_rot, s) => "abcd....\nefgh....\nijkl....\nmnop....\n....ponm\n....lkji\n....hgfe\n....dcba"

Note

• The form of the parameter fct in oper changes according to the language. You can see each form according to the language in "Your test cases".
• It could be easier to take these katas from number (I) to number (IV)

Forthcoming katas will study other tranformations.