vim script の習作です。 現在のカーソル位置にシェルピンスキーの三角形を挿入します。

sierpinski.vim

"
" 現在のカーソル位置にシェルピンスキーの三角形を挿入する.
"
" MIT Lisence
"
" [使い方]
"
" 1. :source sierpinski.vim
" 2. :Sierpinski
"

function! s:main(...)
    let l:width = s:nth_element(a:000, 0, 32)
    let l:height = s:nth_element(a:000, 1, 32)
    let l:field = s:create_field(l:width, l:height)
    call s:render(l:field)
endfunction

function! s:render(field)
    for y in range(len(a:field))
        execute ":normal i" . a:field[y] . "\n"
    endfor
endfunction

function! s:nth_element(xs, i, default)
    return len(a:xs) <= a:i ? a:default : a:xs[a:i]
endfunction

function! s:create_field(width, height)
    let l:field = []

    for y in range(a:height)
        let l:line = ""
        for x in range(a:width)
            if s:bitwise_xor(x, y) == 0
                let l:line = l:line . "++"
            else
                let l:line = l:line . "  "
            endif
        endfor
        call add(l:field, l:line)
    endfor

    return l:field
endfunction

function! s:bitwise_xor(lhs, rhs)
    let l:lhs_bits = s:integer_to_bits(a:lhs)
    let l:rhs_bits = s:integer_to_bits(a:rhs)
    let l:result_bits = []

    for i in range(len(l:lhs_bits))
        if l:lhs_bits[i] + l:rhs_bits[i] == 2
            call add(l:result_bits, 0)
        else
            call add(l:result_bits, 1)
        endif
    endfor

    return s:bits_to_integer(l:result_bits)
endfunction

function! s:integer_to_bits(x)
    let l:x = a:x
    let l:bits = []

    for i in range(32)
        call insert(l:bits, l:x % 2 == 1, 0)
        let l:x = l:x / 2
    endfor

    return l:bits
endfunction

function! s:bits_to_integer(bits)
    let l:value = 0

    for i in range(len(a:bits))
        let l:value = l:value * 2 + (a:bits[i] == 0)
    endfor

    return l:value
endfunction

command! -nargs=* Sierpinski :call s:main(<f-args>)