(* Title: Pure/General/buffer.ML
Author: Makarius
Scalable text buffers.
*)
signature BUFFER =
sig
type T
val empty: T
val is_empty: T -> bool
val add: string -> T -> T
val content: T -> string
val build: (T -> T) -> T
val build_content: (T -> T) -> string
val output: T -> (string -> unit) -> unit
val markup: Markup.T -> (T -> T) -> T -> T
end;
structure Buffer: BUFFER =
struct
abstype T = Buffer of string list
with
val empty = Buffer [];
fun is_empty (Buffer xs) = null xs;
fun add "" buf = buf
| add x (Buffer xs) = Buffer (x :: xs);
fun content (Buffer xs) = implode (rev xs);
fun build (f: T -> T) = f empty;
fun build_content f = build f |> content;
fun output (Buffer xs) out = List.app out (rev xs);
end;
fun markup m body =
let val (bg, en) = Markup.output m
in add bg #> body #> add en end;
end;