move derivations into a separate module

src/func.rs

@@ -1,6 +1,7 @@
 pub mod classes;
 pub mod clone_func;
 pub mod copy_func;
+pub mod derivations;
 #[cfg(test)]
 pub mod test_suite;
 #[cfg(test)]
@@ -85,16 +86,6 @@ pub trait ApplicativeSeq: Functor {
     ) -> Self::F<'a, B>
     where
         Self: 'a;
-    fn _la2<'a, A: 'a, B: 'a, C: 'a>(
-        f: impl 'a + FnOnce(A, B) -> C,
-        fa: Self::F<'a, A>,
-        fb: Self::F<'a, B>,
-    ) -> Self::F<'a, C>
-    where
-        Self: 'a,
-    {
-        Self::seq(Self::fmap(|a| |b| f(a, b), fa), fb)
-    }
 }
 
 pub trait ApplicativeLA2: Functor {
@@ -105,18 +96,6 @@ pub trait ApplicativeLA2: Functor {
     ) -> Self::F<'a, C>
     where
         Self: 'a;
-    fn _seq<'a, A: 'a, B: 'a>(
-        ff: Self::F<'a, impl 'a + FnOnce(A) -> B>,
-        fa: Self::F<'a, A>,
-    ) -> Self::F<'a, B>
-    where
-        Self: 'a,
-    {
-        Self::la2(|f, a| f(a), ff, fa)
-    }
-    fn _tuple<'a, A: 'a, B: 'a>((fa, fb): (Self::F<'a, A>, Self::F<'a, B>)) -> Self::F<'a, (A, B)> {
-        Self::la2(|a, b| (a, b), fa, fb)
-    }
 }
 
 pub trait ApplicativeTuple: Functor {

src/func/classes/stackless.rs

@@ -1,5 +1,6 @@
 use std::{cell::Cell, rc::Rc};
 
+use crate::func::derivations::*;
 use crate::func::*;
 
 enum EvalTree<'a> {
@@ -29,9 +30,7 @@ impl<'a> EvalTree<'a> {
 
 type StackessDyn<'a, A> = dyn 'a + FnOnce(Box<dyn 'a + FnOnce(A)>) -> Oet<'a>;
 
-pub struct Stackless<'a, A: 'a>(
-    Box<StackessDyn<'a, A>>,
-);
+pub struct Stackless<'a, A: 'a>(Box<StackessDyn<'a, A>>);
 
 fn set_cell<A>(cell: Rc<Cell<Option<A>>>, a: A) {
     if cell.replace(Some(a)).is_some() {
@@ -159,7 +158,7 @@ impl ApplicativeLA2 for StacklessClass {
     where
         Self: 'a,
     {
-        Self::_la2(f, fa, fb)
+        Self::_la2_via_seq(f, fa, fb)
     }
 }
 
@@ -168,7 +167,7 @@ impl ApplicativeTuple for StacklessClass {
     where
         Self: 'a,
     {
-        Self::_tuple((fa, fb))
+        Self::_tuple_via_la2((fa, fb))
     }
 }
 

src/func/derivations.rs

@@ -0,0 +1,64 @@
+use crate::func::*;
+
+pub trait ApplicativeLA2ViaSeq: ApplicativeSeq {
+    fn _la2_via_seq<'a, A: 'a, B: 'a, C: 'a>(
+        f: impl 'a + FnOnce(A, B) -> C,
+        fa: Self::F<'a, A>,
+        fb: Self::F<'a, B>,
+    ) -> Self::F<'a, C>
+    where
+        Self: 'a;
+}
+
+impl<T: ApplicativeSeq> ApplicativeLA2ViaSeq for T {
+    fn _la2_via_seq<'a, A: 'a, B: 'a, C: 'a>(
+        f: impl 'a + FnOnce(A, B) -> C,
+        fa: Self::F<'a, A>,
+        fb: Self::F<'a, B>,
+    ) -> Self::F<'a, C>
+    where
+        Self: 'a,
+    {
+        Self::seq(Self::fmap(|a| |b| f(a, b), fa), fb)
+    }
+}
+
+pub trait ApplicativeSeqViaLA2: ApplicativeLA2 {
+    fn _seq_via_la2<'a, A: 'a, B: 'a>(
+        ff: Self::F<'a, impl 'a + FnOnce(A) -> B>,
+        fa: Self::F<'a, A>,
+    ) -> Self::F<'a, B>
+    where
+        Self: 'a;
+}
+
+impl<T: ApplicativeLA2> ApplicativeSeqViaLA2 for T {
+    fn _seq_via_la2<'a, A: 'a, B: 'a>(
+        ff: Self::F<'a, impl 'a + FnOnce(A) -> B>,
+        fa: Self::F<'a, A>,
+    ) -> Self::F<'a, B>
+    where
+        Self: 'a,
+    {
+        Self::la2(|f, a| f(a), ff, fa)
+    }
+}
+
+pub trait ApplicativeTupleViaLA2: ApplicativeLA2 {
+    fn _tuple_via_la2<'a, A: 'a, B: 'a>(
+        fab: (Self::F<'a, A>, Self::F<'a, B>),
+    ) -> Self::F<'a, (A, B)>
+    where
+        Self: 'a;
+}
+
+impl<T: ApplicativeLA2> ApplicativeTupleViaLA2 for T {
+    fn _tuple_via_la2<'a, A: 'a, B: 'a>(
+        (fa, fb): (Self::F<'a, A>, Self::F<'a, B>),
+    ) -> Self::F<'a, (A, B)>
+    where
+        Self: 'a,
+    {
+        Self::la2(|a, b| (a, b), fa, fb)
+    }
+}