1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
|
/*
* esodata - data structures and other things, of varying utility
* Copyright 2022, Ben Culkin
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
package bjc.optics;
import static bjc.optics.Lenses.immutable;
import java.util.function.*;
import bjc.typeclasses.BiContainer;
/**
* A type-invariant var Laarhoven lens.
*
* @author bjcul
*
* @param <Whole> The item this lens can focus on
* @param <Part> The field this lens focuses on
*/
public interface Lens<Whole, Part>
extends LensX<Whole, Whole, Part, Part>, BiContainer<Whole, Part, Lens<Whole, Part>> {
/**
* Modify a given whole using an operation
*
* @param source The whole to modify.
* @param mod The operation to use for modifying a part
*
* @return A modified whole
*/
default Whole modify(Whole source, UnaryOperator<Part> mod) {
return set(source, mod.apply(get(source)));
}
/**
* Create a function which sets the part of a given whole.
*
* @param part The part to set
*
* @return A function that sets the given part on a whole.
*/
default Function<Whole, Whole> setting(Part part) {
return (whole) -> set(whole, part);
}
/**
* Lift a function that modifies parts to one that modifies wholes.
*
* @param f The function which operates on parts
*
* @return A corresponding function which applies the given modification to a
* part.
*/
default Function<Whole, Whole> lift(UnaryOperator<Part> f) {
// modify will be more efficient for some lenses
return (whole) -> modify(whole, f);
}
/**
* Compose two type-variant lenses together.
*
* @param <V1> The first type the second lens focuses on
* @param <V2> The second type the second lens focuses on.
*
* @param other The second lens to use.
*
* @return A lens composed from this one and the given one.
*/
default <V1> Lens<Whole, V1> compose(Lens<Part, V1> other) {
LensX<Whole, Whole, V1, V1> lensX = immutable((whole) -> other.get(get(whole)),
(whole, part) -> update(whole, (val2) -> other.set(val2, part)));
// Note: if lensX is inlined, then the setter function for the lens has to be
// externalized, otherwise type-inference goes BOOM and everything fails.
// Should ask on stack overflow why that is
return (Lens<Whole, V1>) lensX;
}
}
|
