From 433ce13a14fb2c4732d5c0cbda176b25613b1c15 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fran=C3=A7ois=20Garillot?= <francois@garillot.net>
Date: Fri, 16 Apr 2021 17:56:49 -0400
Subject: [PATCH] Add implementations of `From<iXXX>` for prime fields as well

---
 ff/Cargo.toml               |  1 +
 ff/src/fields/arithmetic.rs | 45 +++++++++++++++++++++++++++++++++----
 ff/src/fields/macros.rs     | 10 ++++-----
 3 files changed, 47 insertions(+), 9 deletions(-)

diff --git a/ff/Cargo.toml b/ff/Cargo.toml
index 56939ca93..4a51ec433 100644
--- a/ff/Cargo.toml
+++ b/ff/Cargo.toml
@@ -20,6 +20,7 @@ ark-std = { version = "0.2.0", default-features = false }
 ark-serialize = { version = "^0.2.0", path = "../serialize", default-features = false }
 derivative = { version = "2", features = ["use_core"] }
 num-traits = { version = "0.2", default-features = false }
+paste = "1.0"
 rayon = { version = "1", optional = true }
 zeroize = { version = "1", default-features = false, features = ["zeroize_derive"] }
 
diff --git a/ff/src/fields/arithmetic.rs b/ff/src/fields/arithmetic.rs
index 34924103b..ec5963b8b 100644
--- a/ff/src/fields/arithmetic.rs
+++ b/ff/src/fields/arithmetic.rs
@@ -222,7 +222,7 @@ macro_rules! impl_prime_field_standard_sample {
 }
 
 macro_rules! impl_prime_field_from_int {
-    ($field: ident, u128, $params: ident, $limbs:expr) => {
+    ($field: ident, 128, $params: ident, $limbs:expr) => {
         impl<P: $params> From<u128> for $field<P> {
             fn from(other: u128) -> Self {
                 let mut default_int = P::BigInt::default();
@@ -242,10 +242,22 @@ macro_rules! impl_prime_field_from_int {
                 Self::from_repr(default_int).unwrap()
             }
         }
+
+        impl <P: $params> From<i128> for $field<P> {
+            fn from(other: i128) -> Self {
+                let positive = other.is_positive();
+                let abs = Self::from(other.unsigned_abs());
+                if positive {
+                    abs
+                } else {
+                    -abs
+                }
+            }
+        }
     };
-    ($field: ident, $int: ident, $params: ident, $limbs:expr) => {
-        impl<P: $params> From<$int> for $field<P> {
-            fn from(other: $int) -> Self {
+    ($field: ident, bool, $params: ident, $limbs:expr) => {
+        impl<P: $params> From<bool> for $field<P> {
+            fn from(other: bool) -> Self {
                 if $limbs == 1 {
                     Self::from_repr(P::BigInt::from(u64::from(other) % P::MODULUS.0[0])).unwrap()
                 } else {
@@ -254,6 +266,31 @@ macro_rules! impl_prime_field_from_int {
             }
         }
     };
+    ($field: ident, $int: expr, $params: ident, $limbs:expr) => {
+        paste::paste!{
+            impl<P: $params> From<[<u $int>]> for $field<P> {
+                fn from(other: [<u $int>]) -> Self {
+                    if $limbs == 1 {
+                        Self::from_repr(P::BigInt::from(u64::from(other) % P::MODULUS.0[0])).unwrap()
+                    } else {
+                        Self::from_repr(P::BigInt::from(u64::from(other))).unwrap()
+                    }
+                }
+            }
+
+            impl<P: $params> From<[<i $int>]> for $field<P> {
+                fn from(other: [<i $int>]) -> Self {
+                    let positive = other.is_positive();
+                    let abs = Self::from(other.unsigned_abs());
+                    if positive {
+                        abs
+                    } else {
+                        -abs
+                    }
+                }
+            }
+        }
+    };
 }
 
 macro_rules! sqrt_impl {
diff --git a/ff/src/fields/macros.rs b/ff/src/fields/macros.rs
index 09ccf9e42..4fbc434aa 100644
--- a/ff/src/fields/macros.rs
+++ b/ff/src/fields/macros.rs
@@ -530,11 +530,11 @@ macro_rules! impl_Fp {
             }
         }
 
-        impl_prime_field_from_int!($Fp, u128, $FpParameters, $limbs);
-        impl_prime_field_from_int!($Fp, u64, $FpParameters, $limbs);
-        impl_prime_field_from_int!($Fp, u32, $FpParameters, $limbs);
-        impl_prime_field_from_int!($Fp, u16, $FpParameters, $limbs);
-        impl_prime_field_from_int!($Fp, u8, $FpParameters, $limbs);
+        impl_prime_field_from_int!($Fp, 128, $FpParameters, $limbs);
+        impl_prime_field_from_int!($Fp, 64, $FpParameters, $limbs);
+        impl_prime_field_from_int!($Fp, 32, $FpParameters, $limbs);
+        impl_prime_field_from_int!($Fp, 16, $FpParameters, $limbs);
+        impl_prime_field_from_int!($Fp, 8, $FpParameters, $limbs);
         impl_prime_field_from_int!($Fp, bool, $FpParameters, $limbs);
 
         impl_prime_field_standard_sample!($Fp, $FpParameters);