refactor(operator): replace vec! allocations with array literals in init (#44)

Author: ashyanSpada

.jules/bolt.md

@@ -0,0 +1,3 @@
+## 2024-05-24 - Avoid vec! for constant collections in initialization loops
+**Learning:** Initializing maps/operator managers by iterating over `vec![...]` causes unnecessary heap allocations. Using array literals `[...]` is significantly more efficient since the size is known at compile time and the arrays can be stack-allocated or embedded directly into the binary.
+**Action:** Always prefer iterating over array literals instead of `vec![...]` for statically known collections, especially in hot paths or initialization loops.

benches/display_expression.rs

@@ -1,4 +1,4 @@
-use criterion::{criterion_group, criterion_main, Criterion, black_box};
+use criterion::{black_box, criterion_group, criterion_main, Criterion};
 use expression_engine::{parse_expression, ExprAST};
 
 fn bench_display_expression(c: &mut Criterion) {

src/operator.rs

@@ -57,7 +57,8 @@ impl InfixOpManager {
         use InfixOpType::*;
         self.register("=", 20, SETTER, RIGHT, Arc::new(|_, right| Ok(right)));
 
-        for op in vec!["+=", "-=", "*=", "/=", "%="] {
+        // Iterate over an array literal `[...]` instead of `vec![...]` to avoid heap allocations
+        for op in ["+=", "-=", "*=", "/=", "%="] {
             self.register(
                 op,
                 20,
@@ -88,7 +89,7 @@ impl InfixOpManager {
             );
         }
 
-        for op in vec!["<<=", ">>=", "&=", "^=", "|="] {
+        for op in ["<<=", ">>=", "&=", "^=", "|="] {
             self.register(
                 op,
                 20,
@@ -109,7 +110,7 @@ impl InfixOpManager {
             );
         }
 
-        for (op, precedence) in vec![("||", 40), ("&&", 50)] {
+        for (op, precedence) in [("||", 40), ("&&", 50)] {
             self.register(
                 op,
                 precedence,
@@ -127,7 +128,7 @@ impl InfixOpManager {
             );
         }
 
-        for op in vec!["<", "<=", ">", ">="] {
+        for op in ["<", "<=", ">", ">="] {
             self.register(
                 op,
                 60,
@@ -148,7 +149,7 @@ impl InfixOpManager {
             );
         }
 
-        for op in vec!["==", "!="] {
+        for op in ["==", "!="] {
             self.register(
                 op,
                 60,
@@ -166,7 +167,7 @@ impl InfixOpManager {
             );
         }
 
-        for (op, precedence) in vec![("|", 70), ("^", 80), ("&", 90), ("<<", 100), (">>", 100)] {
+        for (op, precedence) in [("|", 70), ("^", 80), ("&", 90), ("<<", 100), (">>", 100)] {
             self.register(
                 op,
                 precedence,
@@ -187,7 +188,7 @@ impl InfixOpManager {
             );
         }
 
-        for (op, precedence) in vec![("+", 110), ("-", 110), ("*", 120), ("/", 120), ("%", 120)] {
+        for (op, precedence) in [("+", 110), ("-", 110), ("*", 120), ("/", 120), ("%", 120)] {
             self.register(
                 op,
                 precedence,

src/parser.rs

@@ -52,22 +52,16 @@ impl<'a> fmt::Display for ExprAST<'a> {
             Self::Unary(op, rhs) => {
                 write!(f, "Unary AST: Op: {}, Rhs: {}", op, rhs)
             }
-            Self::Binary(op, lhs, rhs) => write!(
-                f,
-                "Binary AST: Op: {}, Lhs: {}, Rhs: {}",
-                op,
-                lhs,
-                rhs
-            ),
+            Self::Binary(op, lhs, rhs) => {
+                write!(f, "Binary AST: Op: {}, Lhs: {}, Rhs: {}", op, lhs, rhs)
+            }
             Self::Postfix(lhs, op) => {
                 write!(f, "Postfix AST: Lhs: {}, Op: {}", lhs, op,)
             }
             Self::Ternary(condition, lhs, rhs) => write!(
                 f,
                 "Ternary AST: Condition: {}, Lhs: {}, Rhs: {}",
-                condition,
-                lhs,
-                rhs
+                condition, lhs, rhs
             ),
             Self::Reference(name) => write!(f, "Reference AST: reference: {}", name),
             Self::Function(name, params) => {