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use proc_macro;
use proc_macro2::{Span, TokenStream};
use syn;
fn vector_merge_for_tuple_impl(count: usize) -> TokenStream {
let generics: Vec<_> = (0..count)
.map(|id| syn::Ident::new(&format!("A{}", id), Span::/*def*/call_site()))
.collect();
let generics = &generics;
let index: Vec<_> = (0..count)
.map(|id| syn::LitInt::new(id as u64, syn::IntSuffix::None, Span::/*def*/call_site()))
.collect();
let index = &index;
let type_impl = quote!{
impl<#(#generics),*> VectorMerge for (#(#generics,)*)
where
#(#generics: VectorMerge,)*
{
type Item = (#(#generics::Item,)*);
fn contains(&mut self, idx: usize) -> bool {
true #(&& self.#index.contains(idx))*
}
fn lower_bound_index(&mut self, mut idx: usize) -> Option<usize> {
const COUNT: usize = #count;
let mut cnt = 0;
loop {
#(match self.#index.lower_bound_index(idx) {
None => {
// one of the source is out of values
return None;
}
Some(i) => if i == idx {
cnt += 1;
if cnt == COUNT {
// all items agree on the lower bound
return Some(i);
}
} else {
// new lower bound, restart loop
idx = i;
cnt = 1;
},
})*
}
}
fn get_unchecked(&mut self, idx: usize) -> Self::Item {
(#(self.#index.get_unchecked(idx),)*)
}
}
};
type_impl
}
pub fn impl_vector_merge_for_tuple_macro(input: proc_macro::TokenStream) -> Result<TokenStream, String> {
let tuple: syn::ExprTuple = syn::parse(input).map_err(|err| format!("Tuple expected, {}", err))?;
let mut gen = Vec::new();
for expr in tuple.elems {
if let syn::Expr::Lit(expr) = expr {
if let syn::Lit::Int(lit) = expr.lit {
let count = lit.value();
let tuple_impl = vector_merge_for_tuple_impl(count as usize);
gen.push(tuple_impl);
} else {
/* expr.lit
.span()
.error(format!("Invalid literal, tuple of integers required"))
.emit();*/
}
} else {
/*expr.span()
.error(format!("Invalid expression, tuple of integers required."))
.emit();*/
}
}
Ok(quote!{
#(#gen)*
}.into())
}