Use to_bigint to output representation as bigint (#1100)

* WIP to_bigint

* use to_signed_felt where necessary

* correct remaining to_biguint().to_bigint() pattern

* address comments

Author: mfachal

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 #### Upcoming Changes
 
+* Use to_signed_felt as function for felt252 as BigInt within [-P/2, P/2] range and use to_bigint as function for representation as BigInt. [#1100](https://github.com/lambdaclass/cairo-rs/pull/1100)
+
 * Implement hint on field_arithmetic lib [#1090](https://github.com/lambdaclass/cairo-rs/pull/1090)
 
     `BuiltinHintProcessor` now supports the following hints:

felt/src/bigint_felt.rs

@@ -182,14 +182,18 @@ impl FeltOps for FeltBigInt<FIELD_HIGH, FIELD_LOW> {
         self.val.to_str_radix(radix)
     }
 
-    fn to_bigint(&self) -> BigInt {
+    fn to_signed_felt(&self) -> BigInt {
         if self.is_negative() {
             BigInt::from_biguint(num_bigint::Sign::Minus, &*CAIRO_PRIME_BIGUINT - &self.val)
         } else {
             self.val.clone().into()
         }
     }
 
+    fn to_bigint(&self) -> BigInt {
+        self.val.clone().into()
+    }
+
     fn to_biguint(&self) -> BigUint {
         self.val.clone()
     }

felt/src/lib.rs

@@ -65,6 +65,10 @@ pub(crate) trait FeltOps {
     /// let negative = Felt252::max_value();
     /// assert_eq!(negative.to_bigint(), Into::<num_bigint::BigInt>::into(-1));
     /// ```
+    fn to_signed_felt(&self) -> BigInt;
+
+    // Converts [`Felt252`]'s representation directly into a [`BigInt`].
+    // Equivalent to doing felt.to_biguint().to_bigint().
     fn to_bigint(&self) -> BigInt;
 
     /// Converts [`Felt252`] into a [`BigUint`] number.
@@ -194,10 +198,17 @@ impl Felt252 {
     pub fn to_str_radix(&self, radix: u32) -> String {
         self.value.to_str_radix(radix)
     }
+
+    pub fn to_signed_felt(&self) -> BigInt {
+        #[allow(deprecated)]
+        self.value.to_signed_felt()
+    }
+
     pub fn to_bigint(&self) -> BigInt {
         #[allow(deprecated)]
         self.value.to_bigint()
     }
+
     pub fn to_biguint(&self) -> BigUint {
         #[allow(deprecated)]
         self.value.to_biguint()

src/hint_processor/builtin_hint_processor/bigint.rs

@@ -50,8 +50,8 @@ pub fn bigint_pack_div_mod_hint(
             d2: x_bigint5.d2,
         };
         let x_lower = x_lower.pack86().to_bigint().unwrap_or_default();
-        let d3 = x_bigint5.d3.as_ref().to_biguint().to_bigint().unwrap();
-        let d4 = x_bigint5.d4.as_ref().to_biguint().to_bigint().unwrap();
+        let d3 = x_bigint5.d3.as_ref().to_bigint();
+        let d4 = x_bigint5.d4.as_ref().to_bigint();
         x_lower + d3 * BigInt::from(BASE.pow(3)) + d4 * BigInt::from(BASE.pow(4))
     };
     let y: BigInt = BigInt3::from_var_name("y", vm, ids_data, ap_tracking)?

src/hint_processor/builtin_hint_processor/math_utils.rs

@@ -478,12 +478,9 @@ pub fn signed_div_rem(
         _ => {}
     }
 
-    #[allow(deprecated)]
-    let int_value = value.to_bigint();
-    #[allow(deprecated)]
-    let int_div = div.to_bigint();
-    #[allow(deprecated)]
-    let int_bound = bound.to_bigint();
+    let int_value = value.to_signed_felt();
+    let int_div = div.to_signed_felt();
+    let int_bound = bound.to_signed_felt();
     let (q, r) = int_value.div_mod_floor(&int_div);
 
     if int_bound.abs() < q.abs() {

src/hint_processor/builtin_hint_processor/secp/bigint_utils.rs

@@ -93,7 +93,7 @@ impl BigInt3<'_> {
         limbs
             .into_iter()
             .enumerate()
-            .map(|(idx, value)| value.to_bigint().shl(idx * 86))
+            .map(|(idx, value)| value.to_signed_felt().shl(idx * 86))
             .sum()
     }
 

src/hint_processor/builtin_hint_processor/secp/secp_utils.rs

@@ -100,7 +100,7 @@ pub(crate) fn bigint3_pack(num: Uint384) -> num_bigint::BigInt {
     limbs
         .into_iter()
         .enumerate()
-        .map(|(idx, value)| value.to_bigint().shl(idx * 86))
+        .map(|(idx, value)| value.to_signed_felt().shl(idx * 86))
         .sum()
 }
 

src/vm/runners/builtin_runner/ec_op.rs

@@ -10,7 +10,7 @@ use crate::vm::errors::runner_errors::RunnerError;
 use crate::vm::vm_memory::memory::Memory;
 use crate::vm::vm_memory::memory_segments::MemorySegmentManager;
 use felt::Felt252;
-use num_bigint::{BigInt, ToBigInt};
+use num_bigint::BigInt;
 use num_integer::{div_ceil, Integer};
 use num_traits::{Num, One, Pow, Zero};
 
@@ -65,35 +65,9 @@ impl EcOpBuiltinRunner {
         prime: &BigInt,
         height: u32,
     ) -> Result<(BigInt, BigInt), RunnerError> {
-        let mut slope = m
-            .clone()
-            .to_biguint()
-            .to_bigint()
-            .ok_or(RunnerError::FoundNonInt)?;
-        let mut partial_sum_b = (
-            partial_sum
-                .0
-                .to_biguint()
-                .to_bigint()
-                .ok_or(RunnerError::FoundNonInt)?,
-            partial_sum
-                .1
-                .to_biguint()
-                .to_bigint()
-                .ok_or(RunnerError::FoundNonInt)?,
-        );
-        let mut doubled_point_b = (
-            doubled_point
-                .0
-                .to_biguint()
-                .to_bigint()
-                .ok_or(RunnerError::FoundNonInt)?,
-            doubled_point
-                .1
-                .to_biguint()
-                .to_bigint()
-                .ok_or(RunnerError::FoundNonInt)?,
-        );
+        let mut slope = m.to_bigint();
+        let mut partial_sum_b = (partial_sum.0.to_bigint(), partial_sum.1.to_bigint());
+        let mut doubled_point_b = (doubled_point.0.to_bigint(), doubled_point.1.to_bigint());
         for _ in 0..height {
             if (doubled_point_b.0.clone() - partial_sum_b.0.clone()).is_zero() {
                 #[allow(deprecated)]

src/vm/vm_core.rs

@@ -937,7 +937,7 @@ impl VirtualMachine {
                 .get(&Relocatable::from((segment_index as isize, i)))
             {
                 Some(val) => match val.as_ref() {
-                    MaybeRelocatable::Int(num) => format!("{}", num.to_bigint()),
+                    MaybeRelocatable::Int(num) => format!("{}", num.to_signed_felt()),
                     MaybeRelocatable::RelocatableValue(rel) => format!("{}", rel),
                 },
                 _ => "<missing>".to_string(),