40: Add solution for Rust track exercise "Grains".

Dependencies

• [2] QK6XE5XF 13: Add Rust track exercises "Beer Song", "Proverb", "Difference Of Squares", "Sum Of Multiples", "Grains", "Prime Factors", "Armstrong Numbers" and "Reverse String".

Change contents

• replacement in rust/grains/tests/grains.rs at line 2
  [2.24314]→[2.24314:24363](∅→∅)
  − assert_eq!(grains::square(input), expected);
  [2.24314]

  [2.24363]
  + assert_eq!(grains::square(input), expected);
• edit in rust/grains/tests/grains.rs at line 6
  [2.24374]

  [2.24374]
  + #[ignore]
• replacement in rust/grains/tests/grains.rs at line 9
  [2.24394]→[2.24394:24425](∅→∅)
  − process_square_case(1, 1);
  [2.24394]

  [2.24425]
  + process_square_case(1, 1);
• replacement in rust/grains/tests/grains.rs at line 16
  [2.24466]→[2.24466:24497](∅→∅)
  − process_square_case(2, 2);
  [2.24466]

  [2.24497]
  + process_square_case(2, 2);
• replacement in rust/grains/tests/grains.rs at line 23
  [2.24538]→[2.24538:24569](∅→∅)
  − process_square_case(3, 4);
  [2.24538]

  [2.24569]
  + process_square_case(3, 4);
• replacement in rust/grains/tests/grains.rs at line 30
  [2.24610]→[2.24610:24641](∅→∅)
  − process_square_case(4, 8);
  [2.24610]

  [2.24641]
  + process_square_case(4, 8);
• replacement in rust/grains/tests/grains.rs at line 38
  [2.24690]→[2.24690:24727](∅→∅)
  − process_square_case(16, 32_768);
  [2.24690]

  [2.24727]
  + process_square_case(16, 32_768);
• replacement in rust/grains/tests/grains.rs at line 45
  [2.24770]→[2.24770:24814](∅→∅)
  − process_square_case(32, 2_147_483_648);
  [2.24770]

  [2.24814]
  + process_square_case(32, 2_147_483_648);
• replacement in rust/grains/tests/grains.rs at line 52
  [2.24857]→[2.24857:24913](∅→∅)
  − process_square_case(64, 9_223_372_036_854_775_808);
  [2.24857]

  [2.24913]
  + process_square_case(64, 9_223_372_036_854_775_808);
• replacement in rust/grains/tests/grains.rs at line 59
  [2.25037]→[2.25037:25060](∅→∅)
  − grains::square(0);
  [2.25037]

  [2.25060]
  + grains::square(0);
• replacement in rust/grains/tests/grains.rs at line 66
  [2.25198]→[2.25198:25222](∅→∅)
  − grains::square(65);
  [2.25198]

  [2.25222]
  + grains::square(65);
• replacement in rust/grains/tests/grains.rs at line 72
  [2.25303]→[2.25303:25364](∅→∅)
  − assert_eq!(grains::total(), 18_446_744_073_709_551_615);
  [2.25303]

  [2.25364]
  + assert_eq!(grains::total(), 18_446_744_073_709_551_615);
• replacement in rust/grains/src/lib.rs at line 2
  [2.25446]→[2.25446:25500](∅→∅)
  − unimplemented!("grains of rice on square {}", s);
  [2.25446]

  [2.25500]
  + if (1..=64).contains(&s) {

  + 2_u64.pow(s - 1)

  + } else {

  + panic!("Square must be between 1 and 64");

  + }
• replacement in rust/grains/src/lib.rs at line 10
  [2.25527]→[2.25527:25549](∅→∅)
  − unimplemented!();
  [2.25527]

  [2.25549]
  + (1_u32..=64).map(square).sum()