fun! s:BrailleInit()
	
	" set up the dot-to-key mappings:
	
	" Braille numeric order:
	" 14
	" 25
	" 36
	" 78
	" let s:dots = [ '1', '2', '3', '4', '5', '6', '7', '8' ]
	
	" Home row:
	" ah
	" sj
	" dk
	" fl
	let s:dots = [ 'a', 's', 'd', 'h', 'j', 'k', 'f', 'l' ]

	" graphical (on a US keyboard):
	" 12
	" qw
	" as
	" zx
	"let s:dots = [ '1', 'q', 'a', '2', 'w', 's', 'z', 'x' ]
	
	let s:blank = s:dots[0].s:dots[0]
	
	let s:orderings = []
	" numeric
	call add(s:orderings, [1,2,3,4, 5,6,7,8])
	" top-to-bottom, left-to-right
	call add(s:orderings, [1,2,3,7, 4,5,6,8])
	" left-to-right, top-to-bottom
	call add(s:orderings, [1,4, 2,5, 3,6, 7,8])

	" if 6 or more dots are set, there are too many permutations if you want
	" to set all possible orders
	let s:too_many_to_set_all = 6
endfun

fun! s:LSBBinary(input)
	let n = a:input
	let b = ''
	let i = 0
	while i < 8
		let b .= n % 2
		let n -= n % 2
		let n = n / 2
		let i+=1
	endwhile
	return b
endfun

fun! s:Permute(n)
	if !exists('l:permcache')
		let l:permcache = [ [], [[0]] ]
	endif
	if len(l:permcache) > a:n
		return l:permcache[a:n]
	else
		let newperms = []
		for l in s:Permute(a:n-1)
			let i = 0
			while i < len(l) + 1
				let new = copy(l)
				call insert(new, a:n-1, i)
				call add(newperms, new)
				let i+=1
			endwhile
		endfor
		let l:permcache[a:n] = newperms
		return newperms
	endif
endfun

" returns all permutations of string in keys
fun! s:KeyOrderings(keys)
	let ret = []
	let chars = split(a:keys,'\zs')
	for indexlist in s:Permute(len(chars))
		let k = ''
		for i in indexlist
			let k .= chars[i]
		endfor
		call add(ret, k)
	endfor
	return ret
endfun

" Just make dots typeable in various orders:
fun! s:SomeOrderings(keys)
	let ret = []
	let set = {}
	for char in split(a:keys,'\zs')
		let set[char] = 1
	endfor
	let setdots = []
	let i = 0
	while i < len(s:dots)
		call add(setdots,has_key(set,s:dots[i])?1:0)
		let i += 1
	endwhile
	for ordering in s:orderings
		let newkeys = ''
		for ndot in ordering
			if setdots[ndot-1]
				let newkeys .= s:dots[ndot-1]
			endif
		endfor
		call add(ret,newkeys)
	endfor
	return ret
endfun

fun! BrailleAbbrev()
	call s:BrailleInit()
	let i = 0
	while i < pow(2, len(s:dots))
		if !i
			let keyslist = [ s:blank ]
		else
			let keys = ''
			let bin = s:LSBBinary(i)
			let j = 0
			let setbits = 0
			for bit in split(bin,'\zs')
				if str2nr(bit) == 1
					let keys .= s:dots[j]
					let setbits += 1
				endif
				let j += 1
			endfor
			if setbits < s:too_many_to_set_all
				let keyslist = s:KeyOrderings(keys)
			else
				let keyslist = s:SomeOrderings(keys)
			endif
		endif
		for keys in keyslist
			let abb = ":iab ".keys." ".nr2char(0x2800+i)
			exe abb
		endfor
		let i+=1
	endwhile
endfun