Define polymorphic lenses and compile the runtime library

.gitignore

@@ -0,0 +1,5 @@
+*.cmi
+*.cmo
+*.cma
+*.byte
+rewrite

META

@@ -0,0 +1,3 @@
+version = "0.1.0"
+description = "Record accessors and composable lenses"
+archive(byte) = "fieldglass.cma"

Makefile

@@ -0,0 +1,20 @@
+OCAMLC ?= ocamlc
+
+.PHONY: all test clean
+all: fieldglass.cma
+
+fieldglass.cmi: fieldglass.mli
+	$(OCAMLC) -c $<
+
+fieldglass.cmo: fieldglass.ml fieldglass.cmi
+	$(OCAMLC) -c $<
+
+fieldglass.cma: fieldglass.cmo
+	$(OCAMLC) -a $< -o $@
+
+test: all
+	$(OCAMLC) fieldglass.cma runtime.ml -o runtime.byte
+	./runtime.byte
+
+clean:
+	rm -f *.cmi *.cmo *.cma *.byte rewrite

README.md

@@ -0,0 +1,5 @@
+# fieldglass
+
+Lenses for reading and updating immutable data in OCaml.
+
+Build with `make`; run the checks with `make test`.

fieldglass.install

@@ -0,0 +1 @@
+lib: ["fieldglass.cmi" "fieldglass.cma" "fieldglass.mli" "META"]

fieldglass.ml

@@ -0,0 +1,5 @@
+type ('s, 't, 'a, 'b) lens = ('s -> 'a) * ('b -> 's -> 't)
+type ('s, 'a) lens' = ('s, 's, 'a, 'a) lens
+
+let lens ~view ~set = view, set
+let view (get, _) = get

fieldglass.mli

@@ -0,0 +1,5 @@
+type ('s, 't, 'a, 'b) lens = ('s -> 'a) * ('b -> 's -> 't)
+type ('s, 'a) lens' = ('s, 's, 'a, 'a) lens
+
+val lens : view:('s -> 'a) -> set:('b -> 's -> 't) -> ('s, 't, 'a, 'b) lens
+val view : ('s, 't, 'a, 'b) lens -> 's -> 'a

fieldglass.opam

@@ -0,0 +1,11 @@
+opam-version: "1.2"
+name: "fieldglass"
+version: "0.1.0"
+maintainer: "rack"
+authors: ["rack"]
+homepage: "https://github.com/rackquiem/fieldglass"
+bug-reports: "https://github.com/rackquiem/fieldglass/issues"
+dev-repo: "git+https://github.com/rackquiem/fieldglass.git"
+build: [make]
+build-test: [make "test"]
+available: [ocaml-version = "4.06.1"]

runtime.ml

@@ -0,0 +1,6 @@
+open Fieldglass
+
+let sample : (string * bool, string) lens' =
+  lens ~view:fst ~set:(fun value (_, other) -> value, other)
+
+let () = assert (view sample ("colour", true) = "colour")