Ok here is my answer in Kona. For the record I would not characterize the K family (and thus Kona) to be made for code-golfing by the scale at which they are used within the finance sector. In any case, here it is:
f:{(y-#a)_'(!#a)!\:a:((.$_ceil y*%#x)*#j)#j:(x," ")}
I am going to try and explain, more or less, how it functions. Note: in Kona, functions are evaluated right-to-left.
First, we begin with
j:(x," ")
Which essentially just appends an empty space at the end of the string, and is then assigned to the variable j. Moving on, we have the following:
a:((.$_ceil y*%#x)*#j)#j:(x," ")
The part (.$_ceil y*%#x)*#j can be broken down in the following way: #x is the number of elements in x, which in our case, since we are applying it to a string, is the number of characters; followed by y*%#x, which just means we divide our desired length by the number of characters in our string. The _ceil is simply the cealing function, and the .$ is used to turn a floating into an integer (if decimal part is zero). All of it is then multiplied by the length of our j (which again is the string with an empty space at the end), and then named "a". Here is a couple of examples of it in use:
{((.$_ceil y*%#x)*#j)#j:(x," ")}["Hello";12]
"Hello Hello Hello "
{((.$_ceil y*%#x)*#j)#j:(x," ")}["Hello";6]
"Hello Hello "
{((.$_ceil y*%#x)*#j)#j:(x," ")}["Hello";4]
"Hello "
{((.$_ceil y*%#x)*#j)#j:(x," ")}["Hello";15]
"Hello Hello Hello "
Once we have our "a", we consider the following part:
(!#a)!\:a
First off, !#a is a vector of integers from 0 up to (#a)-1 (the length of a); e.g. if a is "Hello " as our third example above, then !#a is simply 0 1 2 3. The !\: is a tad more difficult; the ! in its dyadic form is a rotate function; e.g. 2!"Hello" is "lloHe"; and since our (!#a) is a vector, we use the \: to apply all to our a; for example,
1 2 3!\:"Hello"
("elloH"
"lloHe"
"loHel")
Finally, (y-#a)_' is simply removing the first (y-#a) characters from each row of our column vector a.
Here are a few examples of the whole function in action:
f["Hello";8]
("Hello He"
"ello Hel"
"llo Hell"
"lo Hello"
"o Hello "
" Hello H"
"Hello He"
"ello Hel"
"llo Hell"
"lo Hello"
"o Hello "
" Hello H")
f["Hello";2]
("He"
"el"
"ll"
"lo"
"o "
" H")
f["Hello";15]
("Hello Hello Hel"
"ello Hello Hell"
"llo Hello Hello"
"lo Hello Hello "
"o Hello Hello H"
" Hello Hello He"
"Hello Hello Hel"
"ello Hello Hell"
"llo Hello Hello"
"lo Hello Hello "
"o Hello Hello H"
" Hello Hello He"
"Hello Hello Hel"
"ello Hello Hell"
"llo Hello Hello"
"lo Hello Hello "
"o Hello Hello H"
" Hello Hello He")
f["Hello";5]
("Hello"
"ello "
"llo H"
"lo He"
"o Hel"
" Hell")
I hope everything was clear enough. Anyways the character count (without the f: which was added purely for clarity) is 50; and I am sure if I had a bit more time to think about it I could reduce it quite a lot. For more info on Kona here is the GitHub repository: kevinlawler/kona: Open-source implementation of the K programming language
