refactor(monoid): removing semigroup in favour of using add from std

README.md

@@ -1121,29 +1121,22 @@ An object that has a `combine` function that combines it with another object of
 
 It must obey following rules to be `Semigroup`
 
-1. `a.combine(b).combine(c)` is equivalent to `a.combine(b.combine(c))` (associativity)
+1. `a.add(b).add(c)` is equivalent to `a.add(b.add(c))` (associativity)
 
 ```rust
-use itertools::concat;
+use std::ops::Add;
 
-trait Semigroup {
-    fn combine(&self, b: &Self) -> Self;
-}
-
-impl Semigroup for Vec<i32> {
-    fn combine(&self, b: &Self) -> Vec<i32> {
-        concat(vec![self.clone(), b.clone()])
-    }
+pub trait Semigroup<M>: Add<M> {
 }
 
 assert_eq!(
-    vec![1, 2].combine(&vec![3, 4]),
+    vec![1, 2].add(&vec![3, 4]),
     vec![1, 2, 3, 4],
 ); // passes
 
 assert_eq!(
-    a.combine(&b).combine(&c),
-    a.combine(&b.combine(&c)),
+    a.add(&b).add(&c),
+    a.add(&b.add(&c)),
 ); // passes
 ```
 

fp-core/src/foldable.rs

@@ -1,4 +1,5 @@
 use crate::hkt::HKT;
+use crate::monoid::Monoid;
 
 pub trait Foldable<A, B>: HKT<A, B> {
     fn reduce<F>(b: B, ba: F) -> <Self as HKT<A, B>>::Target

fp-core/src/lib.rs

@@ -14,5 +14,4 @@ pub mod lens;
 pub mod monad;
 pub mod monoid;
 pub mod pure;
-pub mod semigroup;
 pub mod setoid;

fp-core/src/monoid.rs

@@ -1,8 +1,5 @@
 use crate::applicative::Applicative;
 use crate::empty::Empty;
+use std::ops::Add;
 
-trait Monoid<A, F, B>: Empty<A> + Applicative<A, F, B>
-where
-    F: FnOnce(A) -> B,
-{
-}
+pub trait Monoid<M>: Empty<M> + Add<M> {}

fp-examples/src/main.rs

@@ -35,3 +35,7 @@ mod semigroup_example;
 mod setoid_example;
 mod side_effects_example;
 mod type_signature_example;
+
+fn main() {
+    println!("Welcome to fp-core!");
+}

fp-examples/src/semigroup_example.rs

@@ -1,3 +1,6 @@
+/*
+// Note that below are just example code. We no longer use manual semigroup implementation.
+// Instead we favour Add, Mul, Sub and etc from std.
 use fp_core::semigroup::*;
 
 #[test]
@@ -8,3 +11,4 @@ fn semigroup_test() {
     assert_eq!(vec![1, 2].combine(&vec![3, 4]), vec![1, 2, 3, 4],);
     assert_eq!(a.combine(&b).combine(&c), a.combine(&b.combine(&c)),);
 }
+*/