cgp-macro-lib 0.7.0

Context-generic programming core component macros implemented as a library.
Documentation 
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use proc_macro2::TokenStream;
use quote::quote;
use syn::parse::{Parse, ParseStream};
use syn::punctuated::Punctuated;
use syn::token::Comma;
use syn::{Expr, Type};

pub struct ParsePunctuated<T>(pub Punctuated<T, Comma>);

impl<T: Parse> Parse for ParsePunctuated<T> {
    fn parse(input: ParseStream) -> syn::Result<Self> {
        let types = Punctuated::parse_terminated(input)?;
        Ok(ParsePunctuated(types))
    }
}

pub fn make_product_type(input: TokenStream) -> TokenStream {
    let types: ParsePunctuated<Type> = syn::parse2(input).unwrap();

    types.0.iter().rfold(quote! { ε }, |res, item| {
        quote! {
            π< #item , #res >
        }
    })
}

pub fn make_sum_type(input: TokenStream) -> TokenStream {
    let types: ParsePunctuated<Type> = syn::parse2(input).unwrap();

    types.0.iter().rfold(quote! { θ }, |res, item| {
        quote! {
            σ< #item , #res >
        }
    })
}

pub fn make_product_expr(input: TokenStream) -> TokenStream {
    let types: ParsePunctuated<Expr> = syn::parse2(input).unwrap();

    types.0.iter().rfold(quote! { ε }, |res, item| {
        quote! {
            π( #item , #res )
        }
    })
}