feat(const): added constants class

constants class can parse and get physical constants from datafile including value, unit, uncertainity, and reference

src/const/private/const.cpp

@@ -0,0 +1,112 @@
+#include <iostream>
+#include <map>
+#include <vector>
+#include <string>
+#include <fstream>
+#include <set>
+
+#include "const.h"
+
+constants::constants() {
+  loaded_ = false;
+}
+
+constants::constants(const std::string& filename) {
+  loaded_ = initialize(filename);
+}
+
+bool constants::initialize(const std::string& filename) {
+  return load(filename);
+}
+
+constant constants::get(const std::string& name) {
+  return constants_[name];
+}
+
+constant constants::operator[](const std::string& name) const {
+  auto it = constants_.find(name);
+  if (it != constants_.end()) {
+    return it->second;
+  } else {
+    throw std::out_of_range("Constant '" + name + "' not found.");
+  }
+}
+
+bool constants::has(const std::string& name) const {
+  return constants_.find(name) != constants_.end();
+}
+
+std::set<std::string> constants::keys() const {
+  std::set<std::string> keys;
+  for (const auto& pair : constants_) {
+    keys.insert(pair.first);
+  }
+  return keys;
+}
+
+std::string constants::trim(const std::string& str) {
+    size_t first = str.find_first_not_of(" \t");
+    if (first == std::string::npos) return "";
+    size_t last = str.find_last_not_of(" \t");
+    return str.substr(first, last - first + 1);
+}
+bool constants::load(const std::string& filename) {
+    std::ifstream file(filename);
+    std::map<std::string, constant> constants_temp;
+    if (!file.is_open()) {
+        std::cerr << "Error: Unable to open file " << filename << std::endl;
+        return false;
+    }
+
+    std::string line;
+    bool data_section = false;
+    int line_count = 0;
+
+    while (std::getline(file, line)) {
+        line_count++;
+
+        // Detect start of data section (double divider line)
+        if (!data_section) {
+            if (line.find("Symbol") != std::string::npos) {  // Find header row
+                std::getline(file, line);  // Skip dashed divider
+                std::getline(file, line);  // Skip second dashed divider
+                data_section = true;
+            }
+            continue;
+        }
+
+        // Ensure the line is long enough to contain all fields
+        if (line.length() < 125) continue;
+
+        // Define exact column widths from Python script
+        int start = 0;
+
+        std::string symbol       = trim(line.substr(start, col_widths_[0])); start += col_widths_[0];
+        std::string name         = line.substr(start, col_widths_[1]); start += col_widths_[1];
+        std::string valueStr     = line.substr(start, col_widths_[2]); start += col_widths_[2];
+        std::string unit         = trim(line.substr(start, col_widths_[3])); start += col_widths_[3]; // Only trim the unit
+        std::string uncertaintyStr = line.substr(start, col_widths_[4]); start += col_widths_[4];
+        std::string reference    = trim(line.substr(start, col_widths_[5])); // Only trim reference
+
+        // Convert numerical fields safely
+        double value = 0.0, uncertainty = 0.0;
+        try {
+            value = std::stod(valueStr);
+        } catch (...) {
+            std::cerr << "Warning: Invalid value in line " << line_count << ": " << valueStr << std::endl;
+        }
+        try {
+            uncertainty = std::stod(uncertaintyStr);
+        } catch (...) {
+            std::cerr << "Warning: Invalid uncertainty in line " << line_count << ": " << uncertaintyStr << std::endl;
+        }
+
+        // Store in map
+        constants_temp[symbol] = {name, value, uncertainty, unit, reference};
+    }
+
+    file.close();
+    constants_ = constants_temp;
+    loaded_ = true;
+    return true;
+}