The beginning of the System F demo.

demos/system-F-type/.merlin

+B _build
+PKG pprint
+PKG visitors.ppx
+PKG visitors.runtime
+PKG alphaLib

demos/system-F-type/F.cppo.ml

+open AlphaLib
+open Abstraction
+#include "AlphaLibMacros.cppo.ml"
+
+(* In this demo, only type variables are handled via AlphaLib. Term variables
+   are represented as strings. *)
+
+(* Types. *)
+
+type ('fn, 'bn) typ =
+  | TyVar of 'fn
+  | TyArrow of ('fn, 'bn) typ * ('fn, 'bn) typ
+  | TyProduct of ('fn, 'bn) typ * ('fn, 'bn) typ
+  | TyForall of ('bn, ('fn, 'bn) typ) abstraction
+  | TyMu of ('bn, ('fn, 'bn) typ) abstraction
+
+(* Term variables. *)
+
+and var = (string[@opaque])
+
+(* Terms. *)
+
+and ('fn, 'bn) term =
+  | TeVar of var
+  | TeAbs of var * ('fn, 'bn) typ * ('fn, 'bn) term
+  | TeApp of ('fn, 'bn) term * ('fn, 'bn) term
+  | TeLet of var * ('fn, 'bn) term * ('fn, 'bn) term
+  | TeTyAbs of ('bn, ('fn, 'bn) term) abstraction
+  | TeTyApp of ('fn, 'bn) term * ('fn, 'bn) typ
+  | TePair of ('fn, 'bn) term * ('fn, 'bn) term
+  | Teroj of int * ('fn, 'bn) term
+
+(* Visitor generation. *)
+
+  [@@deriving
+
+    visitors { variety = "iter"; public = ["visit_term"; "visit_typ"];
+               ancestors = ["Bn.iter"; "Abstraction.iter"] }
+    ,
+    visitors { variety = "map"; public = ["visit_term"; "visit_typ"];
+               ancestors = ["Bn.map"; "Abstraction.map"] }
+    ,
+    visitors { variety = "endo"; public = ["visit_term"; "visit_typ"];
+               ancestors = ["Bn.endo"; "Abstraction.endo"] }
+    ,
+    visitors { variety = "reduce"; public = ["visit_term"; "visit_typ"];
+               ancestors = ["Bn.reduce"; "Abstraction.reduce"] }
+    ,
+    visitors { variety = "iter2"; public = ["visit_term"; "visit_typ"];
+               ancestors = ["Bn.iter2"; "Abstraction.iter2"] }
+
+  ]
+
+(* Operations based on visitors. *)
+
+type raw_typ =
+  (string, string) typ
+type nominal_typ =
+  (Atom.t, Atom.t) typ
+
+type raw_term =
+  (string, string) term
+type nominal_term =
+  (Atom.t, Atom.t) term
+
+__FA
+FA(typ)
+FA(term)
+
+__FILTER
+FILTER(typ)
+FILTER(term)
+
+__BA
+BA(typ)
+BA(term)
+
+__COPY
+COPY(typ)
+COPY(term)
+
+__SHOW
+SHOW(typ)
+SHOW(term)
+
+__IMPORT
+IMPORT(typ)
+IMPORT(term)
+
+__EXPORT
+EXPORT(typ)
+EXPORT(term)
+
+__SIZE
+SIZE(typ)
+SIZE(term)
+
+__EQUIV
+EQUIV(typ)
+EQUIV(term)
+
+__SUBST(typ, TyVar)
+SUBST(typ, typ)
+SUBST(typ, term)

demos/system-F-type/Main.ml

+module T = F

demos/system-F-type/Makefile

+TARGET := \
+  Main.native
+
+PWD := \
+  $(shell pwd)
+
+ALPHALIB := \
+  `ocamlfind query alphaLib`
+
+OCAMLBUILD := \
+  ocamlbuild \
+  -use-ocamlfind \
+  -classic-display \
+  -plugin-tag 'package(cppo_ocamlbuild)' \
+  -tag "cppo_I($(ALPHALIB))" \
+  -tag "cppo_I($(PWD))" \
+
+# TEMPORARY cppo_I($(PWD)) should not be required
+# TEMPORARY a dependency computation on .cppo.ml files should be carried out
+
+MLI := \
+  $(patsubst %.ml,%.inferred.mli,$(shell ls *.ml | grep -v cppo | grep -v myocamlbuild)) \
+  $(patsubst %.cppo.ml,%.inferred.mli,$(shell ls *.cppo.ml)) \
+
+.PHONY: all test mli processed clean
+
+all:
+	@ $(OCAMLBUILD) $(TARGET)
+
+test: all
+	@ ./$(TARGET)
+
+mli:
+	@ $(OCAMLBUILD) $(MLI)
+
+processed: all
+	make -C _build -f ../Makefile.preprocess F.processed.ml
+
+clean:
+	@ rm -f *~
+	@ rm -f *.processed.ml
+	@ $(OCAMLBUILD) -clean

demos/system-F-type/Makefile.preprocess

+# This Makefile allows running visitors as a preprocessor,
+# so as to inspect the generated code and possibly include
+# it in a TeX document.
+
+# This assumes the visitors package is installed.
+
+# The rewriting command.
+PPX          := `ocamlfind query ppx_deriving`/ppx_deriving \
+                `ocamlfind query visitors`/ppx_deriving_visitors.cma
+REWRITE      := ocamlfind ppx_tools/rewriter -ppx '$(PPX)'
+
+# Use GNU sed to extract the generated code.
+# This requires GNU sed 3.95 or above, I am told.
+SED          := $(shell if command -v gsed >/dev/null ; then echo gsed ; else echo sed ; fi)
+EXTRACT      := $(SED) -e '/VISITORS.BEGIN/,/VISITORS.END/!d;//d'
+
+# Use sed to fix some deficiencies of OCaml's code printer.
+# 0. Force a space after a comma.
+# 1. Replace multiple consecutive spaces with a single space.
+# This will destroy indentation; we restore it afterwards.
+# 2. Force a line break after [in].
+# 3. Force a line break after [->].
+# 4. (Ad hoc.) Force a line break between [= let],
+#    presumably at the beginning of a method definition.
+# 5. Remove the line break between [=] and [object].
+BEAUTIFY     := \
+              | $(SED) -e 's/,/, /g' \
+              | $(SED) -e 's/  / /g' \
+              | $(SED) -e 's/ in / in\n/g' \
+              | $(SED) -e 's/ -> / ->\n/g' \
+              | $(SED) -e 's/= let /=\nlet /g' \
+              | perl -0777 -pe 's/=\n *object/= object/gs' \
+
+# Use ocp-indent to beautify the generated code.
+INDENT       := ocp-indent --config=JaneStreet,match_clause=4
+
+%.processed.ml: %.ml
+	$(REWRITE) $< $(BEAUTIFY) | $(INDENT) > $@

demos/system-F-type/_tags

+true: \
+  debug, \
+  safe_string, \
+  warn(A-4-44), \
+  package(pprint), \
+  package(visitors.ppx), \
+  package(visitors.runtime), \
+  package(alphaLib)

demos/system-F-type/myocamlbuild.ml

+let () =
+  Ocamlbuild_plugin.dispatch (fun phase ->
+    Ocamlbuild_cppo.dispatcher phase
+  )