refactor: Refactor code for readability using Option::then

- Optimized the slicing of the symbol path array in `store.rs` using shorthand syntax.
- Utilized the `.then()` combinator

src/eval/mod.rs

@@ -218,11 +218,7 @@ impl<F: LurkField> IO<F> {
             _ => return None,
         };
 
-        if expr.continuation.tag == crate::tag::ContTag::Emit {
-            Some(expr.value)
-        } else {
-            None
-        }
+        (expr.continuation.tag == crate::tag::ContTag::Emit).then_some(expr.value)
     }
 
     pub fn to_vector(&self, store: &Store<F>) -> Result<Vec<F>, store::Error> {

src/lem/store.rs

@@ -177,7 +177,7 @@ impl<F: LurkField> Store<F> {
         match self.sym_cache.get(path) {
             Some(ptr_cache) => *ptr_cache,
             None => {
-                let tail = &path[1..path.len()];
+                let tail = &path[1..];
                 let tail_ptr = self.intern_symbol_path(tail);
                 let head = &path[0];
                 let head_ptr = self.intern_string(head);

src/proof/groth16.rs

@@ -431,8 +431,7 @@ mod tests {
             check_cs_deltas(&cs, limit, lang_rc.clone());
         }
 
-        let proof_results = if check_groth16 {
-            Some(
+        let proof_results = (check_groth16).then(|| 
                 groth_prover
                     .outer_prove(
                         groth_params,
@@ -445,10 +444,7 @@ mod tests {
                         lang_rc,
                     )
                     .unwrap(),
-            )
-        } else {
-            None
-        };
+            );
 
         if let Some((proof, public_inputs, public_outputs)) = proof_results {
             let srs_vk = INNER_PRODUCT_SRS.specialize_vk(proof.proof_count);