define and implement the Incrementable trait for uints

primitive-types/src/lib.rs

@@ -27,7 +27,7 @@ use core::convert::TryFrom;
 use fixed_hash::{construct_fixed_hash, impl_fixed_hash_conversions};
 #[cfg(feature = "scale-info")]
 use scale_info_crate::TypeInfo;
-use uint::{construct_uint, uint_full_mul_reg};
+use uint::{construct_uint, uint_full_mul_reg, Incrementable};
 
 /// Error type for conversion.
 #[derive(Debug, PartialEq, Eq)]

uint/examples/modular.rs

@@ -8,6 +8,7 @@
 
 #[macro_use]
 extern crate uint;
+use uint::Incrementable;
 
 construct_uint! {
 	pub struct U256(4);

uint/src/uint.rs

@@ -127,6 +127,25 @@ impl From<FromHexError> for FromStrRadixErr {
 	}
 }
 
+/// A trait representing an incrementable type.
+///
+/// The `increment` and `initial_value` functions are fallible.
+/// They should either both return `Some` with a valid value, or `None`.
+pub trait Incrementable
+	where
+		Self: Sized,
+{
+	/// Increments the value.
+	///
+	/// Returns `Some` with the incremented value if it is possible, or `None` if it is not.
+	fn increment(&self) -> Option<Self>;
+
+	/// Returns the initial value.
+	///
+	/// Returns `Some` with the initial value if it is available, or `None` if it is not.
+	fn initial_value() -> Option<Self>;
+}
+
 /// Conversion from decimal string error
 #[derive(Debug, PartialEq, Eq)]
 pub enum FromDecStrErr {
@@ -493,6 +512,16 @@ macro_rules! construct_uint {
 				}
 			}
 
+			impl Incrementable for $name {
+				fn increment(&self) -> Option<Self> {
+					self.checked_add(Self::one())
+				}
+
+				fn initial_value() -> Option<Self> {
+					Some(Self::zero())
+				}
+			}
+
 			impl $name {
 				/// Low 2 words (u128)
 				#[inline]

uint/tests/uint_tests.rs

@@ -8,7 +8,7 @@
 
 use core::{convert::TryInto, str::FromStr, u64::MAX};
 use crunchy::unroll;
-use uint::{construct_uint, overflowing, FromDecStrErr};
+use uint::{construct_uint, overflowing, FromDecStrErr, Incrementable};
 
 construct_uint! {
 	pub struct U256(4);
@@ -1192,9 +1192,20 @@ fn bit_assign() {
 	check(U256::MAX, U256::zero());
 }
 
+#[test]
+fn increment() {
+	assert_eq!(U256::from(0).increment(), Some(1.into()));
+	assert_eq!(U256::max_value().increment(), None);
+	assert_eq!(U256::initial_value(), Some(0.into()));
+
+	assert_eq!(U512::from(0).increment(), Some(1.into()));
+	assert_eq!(U512::max_value().increment(), None);
+	assert_eq!(U512::initial_value(), Some(0.into()));
+}
+
 #[cfg(feature = "quickcheck")]
 pub mod laws {
-	use super::construct_uint;
+	use super::{construct_uint, Incrementable};
 	macro_rules! uint_laws {
 		($mod_name:ident, $uint_ty:ident) => {
 			mod $mod_name {