Adding functions to zip slice structures with itertools's izip (which…

… is reexported)

macros/src/generate/world.rs

@@ -838,6 +838,22 @@ fn section_archetype(archetype_data: &DataArchetype) -> TokenStream {
             }
         }
 
+        impl<'a> #ArchetypeSlices<'a> {
+            #[inline(always)]
+            pub fn zipped(
+                &'a self,
+            ) -> impl Iterator<Item = (&'a Entity<#Archetype>, #(&'a #Component),*)> {
+                ::gecs::__internal::izip!(self.entity.iter(), #(self.#component.iter()),*)
+            }
+
+            #[inline(always)]
+            pub fn zipped_mut(
+                &'a mut self,
+            ) -> impl Iterator<Item = (&'a Entity<#Archetype>, #(&'a mut #Component),*)> {
+                ::gecs::__internal::izip!(self.entity.iter(), #(self.#component.iter_mut()),*)
+            }
+        }
+
         impl<'a> ArchetypeCanResolve<'a, #ArchetypeView<'a>, Entity<#Archetype>> for #Archetype {
             #[inline(always)]
             fn resolve_for(&self, key: Entity<#Archetype>) -> Option<usize> {

src/archetype/slices.rs

@@ -4,7 +4,7 @@ use crate::entity::Entity;
 use crate::traits::Archetype;
 
 macro_rules! declare_slices_n {
-    ($slices:ident, $slices_mut:ident, $n:literal) => {
+    ($slices:ident, $n:literal) => {
         seq!(I in 0..$n {
             pub trait $slices<'a, A: Archetype, #(T~I,)*> {
                 fn new(entities: &'a [Entity<A>], #(s~I: &'a mut [T~I],)*) -> Self;
@@ -15,11 +15,11 @@ macro_rules! declare_slices_n {
 
 // Declare slices for up to 16 components.
 seq!(N in 1..=16 {
-    declare_slices_n!(Slices~N, SlicesMut~N, N);
+    declare_slices_n!(Slices~N, N);
 });
 
 // Declare additional slices for up to 32 components.
 #[cfg(feature = "32_components")]
 seq!(N in 17..=32 {
-    declare_slices_n!(Slices~N, SlicesMut~N, N);
+    declare_slices_n!(Slices~N, N);
 });

src/lib.rs

@@ -801,4 +801,7 @@ pub mod __internal {
     pub use traits::{World, WorldHas};
     pub use traits::{Archetype, ArchetypeHas};
     pub use traits::{View, ViewHas};
+
+
+    pub use itertools::izip as izip;
 }