56 lines
1.9 KiB
OCaml
56 lines
1.9 KiB
OCaml
(** {1 Micro pre-processor for Heptagon}
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This module uses camlp4 to replace some fixed strings by string literals at
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compile-time. At the moment, we only replace DATE by the current date and
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STDLIB by "../../lib". Each pseudo-variable can be overriden by the
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environment variable of the same name. *)
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open Camlp4.PreCast
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open Unix
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(** {2 Compile-time strings} *)
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(** [date] is a string denoting the current date. *)
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let date =
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let days = [| "sunday"; "monday"; "tuesday"; "wednesday"; "thursday";
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"friday"; "saturday" |]
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and months = [| "january"; "february"; "march"; "april"; "may"; "june";
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"july"; "august"; "september"; "october"; "november";
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"december" |] in
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let tm = Unix.localtime (Unix.gettimeofday ()) in
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let (day, month) =
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let prefix s = String.sub s 0 3 in
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(prefix days.(tm.tm_wday), prefix months.(tm.tm_mon)) in
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Format.sprintf "%s. %s. %d %d:%d:%d CET %d"
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day month tm.tm_mday tm.tm_hour tm.tm_min tm.tm_sec (1900 + tm.tm_year)
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(** [stdlib] is the location of the standard Heptagon library. *)
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let stdlib =
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let wd = Unix.getcwd () in
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Filename.concat (Filename.dirname (Filename.dirname wd)) "lib"
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(** Association list defining bindings between constant and our "compile-time
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constants". *)
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let env = [("DATE", date); ("STDLIB", stdlib)]
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(** {2 Camlp4 hook} *)
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(** Our home-grown super-duper syntax filter. Looks for string constants present
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in [subst] and replaces them according to the couple found in the
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environment defined above. *)
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let filter =
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object
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inherit Ast.map as super
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method expr e = match e with
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| <:expr< $str:s$ >> when List.mem_assoc s env ->
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let repl = try Sys.getenv s with Not_found -> List.assoc s env in
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<:expr@here< $str:repl$ >>
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| x -> x
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end;;
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(** Tell Camlp4 about it. *)
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AstFilters.register_str_item_filter filter#str_item
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