[Preliminary Pull Request] Use LambdaWorks' FieldElement in stark-felt crate

crates/stark-felt/Cargo.toml

@@ -13,8 +13,14 @@ readme = "README.md"
 [dependencies]
 bitvec = { version = "1.0.1", default-features = false }
 serde = { version = "1.0.163", optional = true, default-features = false }
-
+# TODO: use version once published
+# lambdaworks-math = { version = "0.1.1", default-features = false }
+lambdaworks-math = { git = "https://github.com/lambdaclass/lambdaworks.git", rev = "bfd91d4e8116ab8b0bf25f75a9f1e8bb61d355d9", default_features = false}
 [features]
 default = ["std", "serde"]
 std = []
 alloc = ["serde?/alloc"]
+
+[dev-dependencies]
+proptest = "1.1.0"
+serde_test = "1.0.1"

crates/stark-felt/src/arbitrary.rs

@@ -0,0 +1,48 @@
+use lambdaworks_math::{field::element::FieldElement, unsigned_integer::element::UnsignedInteger};
+use proptest::prelude::*;
+
+use crate::Felt;
+const FIELD_HIGH: u128 = (1 << 123) + (17 << 64); // this is equal to 10633823966279327296825105735305134080
+const FIELD_LOW: u128 = 1;
+
+/// Returns a [`Strategy`] that generates any valid Felt
+fn any_felt() -> impl Strategy<Value = Felt> {
+    (0..=FIELD_HIGH)
+        // turn range into `impl Strategy`
+        .prop_map(|x| x)
+        // choose second 128-bit limb capped by first one
+        .prop_flat_map(|high| {
+            let low = if high == FIELD_HIGH {
+                (0..FIELD_LOW).prop_map(|x| x).sboxed()
+            } else {
+                any::<u128>().sboxed()
+            };
+            (Just(high), low)
+        })
+        // turn (u128, u128) into limbs array and then into Felt
+        .prop_map(|(high, low)| {
+            let limbs = [
+                (high >> 64) as u64,
+                (high & ((1 << 64) - 1)) as u64,
+                (low >> 64) as u64,
+                (low & ((1 << 64) - 1)) as u64,
+            ];
+            FieldElement::new(UnsignedInteger::from_limbs(limbs))
+        })
+        .prop_map(Felt)
+}
+
+/// Returns a [`Strategy`] that generates any nonzero Felt
+pub fn nonzero_felt() -> impl Strategy<Value = Felt> {
+    any_felt().prop_filter("is zero", |x| !x.is_zero())
+}
+
+impl Arbitrary for Felt {
+    type Parameters = ();
+
+    fn arbitrary_with(_args: Self::Parameters) -> Self::Strategy {
+        any_felt().sboxed()
+    }
+
+    type Strategy = SBoxedStrategy<Self>;
+}