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WIP: Initial implementation of optional lens #1

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WIP: Initial implementation of optional lens #1

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3 changes: 2 additions & 1 deletion .gitignore
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Original file line number Diff line number Diff line change
Expand Up @@ -3,4 +3,5 @@ lib
.merlin
_opam/
.idea/
.bsb.lock
.bsb.lock
ppx/focus.native
31 changes: 20 additions & 11 deletions bsconfig.json
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Original file line number Diff line number Diff line change
Expand Up @@ -7,19 +7,28 @@
"error": "+8"
},
"sources": [
{"dir": "src"},
{"dir": "ppx", "type": "ppx", "ppx": ["Focus"]},
{"dir": "tests", "type": "dev", "subdirs": true, "ppx": ["Focus"], "backend": "native"}
{ "dir": "src" },
{ "dir": "ppx", "type": "ppx", "ppx": ["Focus"] },
{
"dir": "tests",
"type": "dev",
"subdirs": true,
"ppx": ["Focus"],
"backend": "native"
}
],
"ocaml-dependencies": ["compiler-libs", "unix", "bigarray", "str"],
"public": ["Main"],
"entries": [{
"backend": "native",
"main-module": "Tests"
}, {
"backend": "native",
"type": "ppx",
"main-module": "Focus"
}],
"entries": [
{
"backend": "native",
"main-module": "Tests"
},
{
"backend": "native",
"type": "ppx",
"main-module": "Focus"
}
],
"refmt": 3
}
104 changes: 74 additions & 30 deletions ppx/Focus.re
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Original file line number Diff line number Diff line change
Expand Up @@ -6,17 +6,23 @@ open Ast_helper;

let fail = (loc, txt) => raise(Location.Error(Location.error(~loc, txt)));
let lid = (~loc=default_loc^, s) => mkloc(Longident.parse(s), loc);
let evar = (~loc=?, ~attrs=?, s) => Exp.ident(~loc?, ~attrs?, lid(~loc?, s));
let evar = (~loc=?, ~attrs=?, s) =>
Exp.ident(~loc?, ~attrs?, lid(~loc?, s));

let updated_record = (record, field, value) =>
Exp.mk(
Pexp_record(
[(mknoloc(Lident(field)), Exp.mk(Pexp_ident(mknoloc(Lident(value)))))],
[
(
mknoloc(Lident(field)),
Exp.mk(Pexp_ident(mknoloc(Lident(value)))),
),
],
Some(Exp.mk(Pexp_ident(mknoloc(Lident(record))))),
),
);

let createLens = name => [%expr
let createFieldLens = name => [%expr
{
get: r => [%e Exp.field(evar("r"), mknoloc(Lident(name)))],
set: (v, r) => [%e updated_record("r", name, "v")],
Expand All @@ -26,42 +32,80 @@ let createLens = name => [%expr
let focus_mapper =
Parsetree.{
...Ast_mapper.default_mapper,
expr: (mapper, expr) =>
switch (expr.pexp_desc) {
| Pexp_field(pexp, {txt}) =>
%expr
{
open Lens;
let%e rec recurseField = (
fun
| {pexp_desc: Pexp_field({pexp_desc: Pexp_ident({txt: Lident(name)})}, {txt: Lident(snd_name)})} => {
print_string("base case: \n");
print_string("name: " ++ name);
print_newline();
print_string("snd_name: " ++ snd_name);
print_newline();
expr: (mapper, expr) => [%expr
{
open Lens;
let%e rec recurseField =
fun
| {
pexp_desc:
Pexp_field(
{pexp_desc: Pexp_ident({txt: Lident(name)})},
{txt: Lident(snd_name)},
) |
Pexp_apply(
{pexp_desc: Pexp_ident({txt: Lident("$.")})},
[
(_, {pexp_desc: Pexp_ident({txt: Lident(name)})}),
(_, {pexp_desc: Pexp_ident({txt: Lident(snd_name)})}),
],
),
} => [%expr
[%e createFieldLens(snd_name)]
]
| {
pexp_desc:
Pexp_apply(
{pexp_desc: Pexp_ident({txt: Lident("$.")})},
[
(_, {pexp_desc: Pexp_ident({txt: Lident(name)})}),
(_, next),
],
),
} => {
%expr
[%e recurseField(next)]
}
| {
pexp_desc:
Pexp_field(next, {txt: Lident(name)}) |
Pexp_apply(
{pexp_desc: Pexp_ident({txt: Lident("$.")})},
[
(_, next),
(_, {pexp_desc: Pexp_ident({txt: Lident(name)})}),
],
),
} => [%expr
[%e recurseField(next)] |-- [%e createFieldLens(name)]
]

%expr
[%e createLens(snd_name)];
}
| {pexp_desc: Pexp_field(next, {txt: Lident(name)})} => [%expr
[%e recurseField(next)] |-- [%e createLens(name)]
]
| x => Ast_mapper.default_mapper.expr(mapper, x)
);
| {
pexp_desc:
Pexp_apply(
{pexp_desc: Pexp_ident({txt: Lident("$.")})},
[(_, left), (_, right)],
),
} => [%expr
[%e recurseField(left)] |-? [%e recurseField(right)]
]

recurseField(expr);
}
| _ => fail(expr.pexp_loc, "invalid lens declaration")
},
| x => Ast_mapper.default_mapper.expr(mapper, x);

recurseField(expr);
}
],
};

let mapper = _argv =>
Parsetree.{
...Ast_mapper.default_mapper,
expr: (mapper, expr) =>
switch (expr.pexp_desc) {
| Pexp_extension(({txt: "focus", loc}, PStr([{pstr_desc: Pstr_eval(expr, attributes)}]))) =>
| Pexp_extension((
{txt: "focus", loc},
PStr([{pstr_desc: Pstr_eval(expr, attributes)}]),
)) =>
focus_mapper.expr(focus_mapper, expr)
| _ => Ast_mapper.default_mapper.expr(mapper, expr)
},
Expand Down
32 changes: 31 additions & 1 deletion src/Lens.re
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Expand Up @@ -4,6 +4,11 @@ type t('a, 'b) = {
};

let (|-) = (f, g, x) => g(f(x));
let (|?) = (f, g, x) =>
switch (f(x)) {
| Some(x) => g(x)
| None => None
};

let over = (l, f, a) => {
let value = l.get(a);
Expand All @@ -17,7 +22,32 @@ let modify = (l, f, a) => {
l.set(new_value, a);
};

let compose = (l1, l2) => {get: l2.get |- l1.get, set: l1.set |- modify(l2)};
let flatMap = (f, x) =>
switch (x) {
| Some(x) => f(x)
| None => None
};

let optionalModify = (l, f, a) => {
let value = l.get(a);
switch (value) {
| Some(x) =>
let new_value = f(x);
l.set(Some(new_value), a);
| None => a
};
};

let compose = (l1, l2) => {
get: l2.get |- l1.get,
set: l1.set |- modify(l2),
};

let optional = (l1, l2) => {
get: l2.get |? l1.get,
set: l1.set |- optionalModify(l2),
};

let (--|) = compose;
let (|--) = (l1, l2) => compose(l2, l1);
let (|-?) = (l1, l2) => optional(l2, l1);
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