47 lines
1.1 KiB
Standard ML
47 lines
1.1 KiB
Standard ML
structure PosData =
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struct
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(* I don't like introducing new bindings in the global name space
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* so the pos_data type is introduced in a new struct. *)
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type t = {chr: char, strIdx: int, absIdx: int, hd: string, tl: string list}
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end
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signature MAKE_TEXT_BUILDER =
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sig
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type state
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type env
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val folder: PosData.t * env * state -> state
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val stopFold: state -> bool
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end
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functor MakeTextBuilder(Fn: MAKE_TEXT_BUILDER) =
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struct
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fun buildLoop (strIdx, absIdx, hd, tl, env, state) =
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if Fn.stopFold state then
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state
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else if strIdx = String.size hd then
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case tl of
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hd :: tl => buildLoop (0, absIdx, hd, tl, env, state)
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| [] => state
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else
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let
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val chr = String.sub (hd, strIdx)
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val posData =
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{chr = chr, strIdx = strIdx, absIdx = absIdx, hd = hd, tl = tl}
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val state = Fn.folder (posData, env, state)
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in
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buildLoop (strIdx + 1, absIdx + 1, hd, tl, env, state)
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end
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end
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structure Good =
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MakeTextBuilder
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(struct
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type state = unit
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type env = unit
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fun folder (_, _, _) = ()
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fun stopFold () = false
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fun finish () = 33
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end)
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