Macro int_seq 

int_seq!() { /* proc-macro */ }

Given a sequence of integers that includes an range ellipsis, we deduce the integers that are omitted using various heuristics. This macro will produce an array of integers at compile time. We do not support lazy iterators yet since some integer sequences do not have a simple closed form formula.

We currently use two heuristics for inferring integer sequences:

• Affine sequences are of the form a*i + b
• OEIS sequences are in the On-Line Encyclopedia of Integer Sequences (OEIS) database. We use reqwest to perform HTTP requests within a procedural macro to query the database. By doing this at compile time, we can avoid runtime overheads

This is inspired by Raku lang’s sequence operator (...).

Example:

use int_seq::int_seq;

// affine sequence
assert_eq!(int_seq!(57, 64, 71, 78, 85..100), [57, 64, 71, 78, 85, 92, 99]);
// inclusive upper bound
assert_eq!(int_seq!(3, 6..=12), [3, 6, 9, 12]);
// basic range
assert_eq!(int_seq!(1..5), [1, 2, 3, 4]);
// powers of 2
assert_eq!(int_seq!(1, 2, 4, 8, 16..=1024), [1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024]);
// fibonacci sequence
assert_eq!(int_seq!(0, 1, 1, 2, 3, 5, 8, 13..100), [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89]);
// McKay-Thompson series of class 32e for the Monster group (OEIS A082303).
assert_eq!(int_seq!(-4, -9, 4, 10..26), [-4, -9, 4, 10, -4, -12, 6, 15, -7, -17, 7, 19, -8, -22, 10])