Macro rec_all 

macro_rules! rec_all {
    ($in_list:expr, $($func:tt)*) => { ... };
}

Helper for writing const fn equivalents of NList::all

This macro acts like a function with this signature:

use nlist::{NList, PeanoInt};

use nlist::receiver::Receiver;

fn rec_all<'a, P, T, L, F>(list: P , func: F) -> bool
where
    P: Receiver<'a, NList<T, L>>,
    L: PeanoInt,
    T: 'a,
    F: FnOnce(
        ... // parameter types explained below
    ) -> bool

The closure is only called when the list is non-empty (i.e.: when L != 0).

The closure parameters depend on the value of P:

• If P == NList<T, L>: the parameters are (T, Nlist<T, L::SubOneSat>)
• If P == &NList<T, L>: the parameters are (&T, &Nlist<T, L::SubOneSat>)
• If P == &mut NList<T, L>: the parameters are (&mut T, &mut Nlist<T, L::SubOneSat>)

Note

Because iteration over the list might terminate before the list is fully consumed, by-value iteration over non-Copy types does not work in const, and by-value iteration over Copy types requires doing what the by-value example does.

Example

By reference

Example that takes an NList by reference

use nlist::{NList, Peano, PeanoInt, nlist};
 
const ALL_EVEN: bool = all_even(&nlist![3, 5, 8]);
 
assert!(!ALL_EVEN);
 
const fn all_even<L>(list: &NList<u128, L>) -> bool
where
    L: PeanoInt
{
    nlist::rec_all!{list, |elem: &u128, next| *elem % 2 == 0 && all_even(next)}
}

By value

Example that takes an NList of Copy elements by value

use nlist::{NList, Peano, PeanoInt, nlist};
 
use std::mem::ManuallyDrop as MD;
 
 
const ALL_EMPTY_ARE_ODD: bool = all_odd(nlist![]);
assert!(ALL_EMPTY_ARE_ODD);
 
const ALL_ODD: bool = all_odd(nlist![3, 5, 13]);
assert!(ALL_ODD);
 
const fn all_odd<L>(list: NList<u128, L>) -> bool
where
    L: PeanoInt
{
    nlist::rec_all!{list, |elem: u128, next| {
        // works around "destructor cannot be evaluated at compile-time" error
        let next = next.assert_copy();

        elem % 2 == 1 && all_odd(MD::into_inner(next))
    }}

}