correct remaining to_biguint().to_bigint() pattern

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:

src/hint_processor/builtin_hint_processor/math_utils.rs

@@ -483,7 +483,7 @@ pub fn signed_div_rem(
     #[allow(deprecated)]
     let int_div = div.to_signed_felt();
     #[allow(deprecated)]
-    let int_bound = bound.to_bigint();
+    let int_bound = bound.to_signed_felt();
     let (q, r) = int_value.div_mod_floor(&int_div);
 
     if int_bound.abs() < q.abs() {

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.clone().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)]