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|
signature GENE = sig
val reverse: string -> string
val first: int -> string
val next: string -> string option
end
structure Gene :> GENE = struct
fun reverse s =
let
val n = size s
val m = n - 1
fun opposite c = case c of
#"A" => #"T"
| #"T" => #"A"
| #"C" => #"G"
| #"G" => #"C"
| _ => c
in
CharVector.tabulate (n, fn i => opposite (String.sub (s, m - i)))
end
fun first order = CharVector.tabulate (order, fn _ => #"A")
fun next nmer =
let
val order = size nmer
fun finish (rightmostNonT, replacement) = CharVector.tabulate (
order
, fn index =>
case
Int.compare (
index
, rightmostNonT
)
of
LESS => String.sub (nmer, index)
| EQUAL => replacement
| GREATER => #"A"
)
fun continue index =
if index < 0 then NONE
else case String.sub (nmer, index) of
#"A" => SOME (finish (index, #"C"))
| #"C" => SOME (finish (index, #"G"))
| #"G" => SOME (finish (index, #"T"))
| #"T" => continue (index - 1)
| _ => raise Fail "Invalid base"
in
continue (size nmer - 1)
end
end
|
