fp_library/types/
string.rs

1//! Implementations for [`String`].
2
3use crate::{
4	classes::{monoid::Monoid, semigroup::Semigroup},
5	hkt::Kind1L0T,
6};
7
8impl Kind1L0T for String {
9	type Output<'a> = String;
10}
11
12impl Semigroup for String {
13	/// Appends one string to another.
14	///
15	/// # Type Signature
16	///
17	/// `forall. Semigroup String => (String, String) -> String`
18	///
19	/// # Parameters
20	///
21	/// * `a`: The first string.
22	/// * `b`: The second string.
23	///
24	/// # Returns
25	///
26	/// The concatenated string.
27	///
28	/// # Examples
29	///
30	/// ```
31	/// use fp_library::classes::semigroup::append;
32	///
33	/// assert_eq!(append("Hello, ".to_string(), "World!".to_string()), "Hello, World!".to_string());
34	/// ```
35	fn append(
36		a: Self,
37		b: Self,
38	) -> Self {
39		a + &b
40	}
41}
42
43impl Monoid for String {
44	/// Returns an empty string.
45	///
46	/// # Type Signature
47	///
48	/// `forall. Monoid String => () -> String`
49	///
50	/// # Returns
51	///
52	/// An empty string.
53	///
54	/// # Examples
55	///
56	/// ```
57	/// use fp_library::classes::monoid::empty;
58	///
59	/// assert_eq!(empty::<String>(), "".to_string());
60	/// ```
61	fn empty() -> Self {
62		String::new()
63	}
64}
65
66#[cfg(test)]
67mod tests {
68	use crate::classes::{monoid::Monoid, semigroup::append};
69	use quickcheck_macros::quickcheck;
70
71	// Semigroup Laws
72
73	/// Tests the associativity law for Semigroup.
74	#[quickcheck]
75	fn semigroup_associativity(
76		a: String,
77		b: String,
78		c: String,
79	) -> bool {
80		append(a.clone(), append(b.clone(), c.clone())) == append(append(a, b), c)
81	}
82
83	// Monoid Laws
84
85	/// Tests the left identity law for Monoid.
86	#[quickcheck]
87	fn monoid_left_identity(a: String) -> bool {
88		append(String::empty(), a.clone()) == a
89	}
90
91	/// Tests the right identity law for Monoid.
92	#[quickcheck]
93	fn monoid_right_identity(a: String) -> bool {
94		append(a.clone(), String::empty()) == a
95	}
96}
fp_library/types/string.rs

fp_library/types/
string.rs
