From 9f0f6c111384f2116613ea95d816fa43dc3fc1f3 Mon Sep 17 00:00:00 2001
From: Tyler Veness <calcmogul@gmail.com>
Date: Sat, 11 Jan 2025 14:48:54 -0800
Subject: [PATCH] Replace iterator loops with ranges

---
 include/sleipnir/autodiff/ExpressionGraph.hpp | 28 ++++++++-----------
 src/util/PrintIterationDiagnostics.hpp        |  2 +-
 2 files changed, 13 insertions(+), 17 deletions(-)

diff --git a/include/sleipnir/autodiff/ExpressionGraph.hpp b/include/sleipnir/autodiff/ExpressionGraph.hpp
index 5e9be8de..038cceef 100644
--- a/include/sleipnir/autodiff/ExpressionGraph.hpp
+++ b/include/sleipnir/autodiff/ExpressionGraph.hpp
@@ -2,6 +2,7 @@
 
 #pragma once
 
+#include <ranges>
 #include <span>
 
 #include "sleipnir/autodiff/Expression.hpp"
@@ -42,10 +43,10 @@ class ExpressionGraph {
     // Initialize the number of instances of each node in the tree
     // (Expression::duplications)
     while (!stack.empty()) {
-      auto currentNode = stack.back();
+      auto node = stack.back();
       stack.pop_back();
 
-      for (auto&& arg : currentNode->args) {
+      for (auto&& arg : node->args) {
         // Only continue if the node is not a constant and hasn't already been
         // explored.
         if (arg != nullptr && arg->Type() != ExpressionType::kConstant) {
@@ -62,19 +63,19 @@ class ExpressionGraph {
     stack.emplace_back(root.Get());
 
     while (!stack.empty()) {
-      auto currentNode = stack.back();
+      auto node = stack.back();
       stack.pop_back();
 
       // BFS lists sorted from parent to child.
-      m_rowList.emplace_back(currentNode->row);
-      m_adjointList.emplace_back(currentNode);
-      if (currentNode->args[0] != nullptr) {
+      m_rowList.emplace_back(node->row);
+      m_adjointList.emplace_back(node);
+      if (node->args[0] != nullptr) {
         // Constants (expressions with no arguments) are skipped because they
         // don't need to be updated
-        m_valueList.emplace_back(currentNode);
+        m_valueList.emplace_back(node);
       }
 
-      for (auto&& arg : currentNode->args) {
+      for (auto&& arg : node->args) {
         // Only add node if it's not a constant and doesn't already exist in the
         // tape.
         if (arg != nullptr && arg->Type() != ExpressionType::kConstant) {
@@ -97,9 +98,7 @@ class ExpressionGraph {
   void Update() {
     // Traverse the BFS list backward from child to parent and update the value
     // of each node.
-    for (auto it = m_valueList.rbegin(); it != m_valueList.rend(); ++it) {
-      auto& node = *it;
-
+    for (auto& node : m_valueList | std::views::reverse) {
       auto& lhs = node->args[0];
       auto& rhs = node->args[1];
 
@@ -136,9 +135,7 @@ class ExpressionGraph {
     // Zero adjoints. The root node's adjoint is 1.0 as df/df is always 1.
     if (m_adjointList.size() > 0) {
       m_adjointList[0]->adjointExpr = MakeExpressionPtr<ConstExpression>(1.0);
-      for (auto it = m_adjointList.begin() + 1; it != m_adjointList.end();
-           ++it) {
-        auto& node = *it;
+      for (auto& node : m_adjointList | std::views::drop(1)) {
         node->adjointExpr = MakeExpressionPtr<ConstExpression>();
       }
     }
@@ -194,8 +191,7 @@ class ExpressionGraph {
   void ComputeAdjoints(function_ref<void(int row, double adjoint)> func) {
     // Zero adjoints. The root node's adjoint is 1.0 as df/df is always 1.
     m_adjointList[0]->adjoint = 1.0;
-    for (auto it = m_adjointList.begin() + 1; it != m_adjointList.end(); ++it) {
-      auto& node = *it;
+    for (auto& node : m_adjointList | std::views::drop(1)) {
       node->adjoint = 0.0;
     }
 
diff --git a/src/util/PrintIterationDiagnostics.hpp b/src/util/PrintIterationDiagnostics.hpp
index 3234915f..d02c9791 100644
--- a/src/util/PrintIterationDiagnostics.hpp
+++ b/src/util/PrintIterationDiagnostics.hpp
@@ -69,7 +69,7 @@ void PrintIterationDiagnostics(int iterations, bool feasibilityRestoration,
       }
       constexpr const char* strs[] = {"⁰", "¹", "²", "³", "⁴",
                                       "⁵", "⁶", "⁷", "⁸", "⁹"};
-      for (const auto& digit : std::ranges::views::reverse(digits)) {
+      for (const auto& digit : digits | std::views::reverse) {
         reg += strs[digit];
       }