.

utils/TextFunctions.h

 #pragma once
 
+#include <charconv>
+#include <array>
 #include <iostream>
 #include <sstream>
 #include <fstream>
@@ -15,7 +17,7 @@
 
 #define SPACES " \t\r\n"
 
-static std::string ToStr(const int arg, const int leading_zeros = 0)
+static std::string ToStr(const int arg, const int leading_zeros)
 {
     std::ostringstream ss;
     if(leading_zeros) {
@@ -25,7 +27,7 @@ static std::string ToStr(const int arg, const int leading_zeros = 0)
     return ss.str();
 }
 
-static std::string ToStr(const size_t arg, const int leading_zeros = 0)
+static std::string ToStr(const size_t arg, const int leading_zeros)
 {
     std::ostringstream ss;
     if (leading_zeros) {
@@ -35,13 +37,64 @@ static std::string ToStr(const size_t arg, const int leading_zeros = 0)
     return ss.str();
 }
 
-static std::string ToStr(const double arg)
+template <typename T> 
+void hangle_to_chars_error(const std::to_chars_result& res, const T& arg)
 {
-    std::ostringstream ss;
-    ss << arg;
-    return ss.str();
+    if (res.ec == std::errc::invalid_argument) {
+        throw Exp() << "failed to convert value [" << arg << "] to string, invalid argument";
+    }
+
+    if (res.ec == std::errc::result_out_of_range) {
+        throw Exp() << "failed to convert value [" << arg << "] to string, out of range";
+    }
+
+    throw Exp() << "failed to convert value [" << arg << "] to string";
+}
+
+static std::string ToStr(const int arg)
+{
+    std::array<char, 32> buf;
+
+    const auto res = std::to_chars(buf.data(), buf.data() + buf.size(), arg);
+
+    if (res.ec == std::errc()) {
+        return std::string(buf.data(), res.ptr - buf.data());
+    }
+
+    hangle_to_chars_error(res, arg);
+
+    return "";
 }
 
+static std::string ToStr(const size_t arg)
+{
+    std::array<char, 32> buf;
+
+    const auto res = std::to_chars(buf.data(), buf.data() + buf.size(), arg);
+
+    if (res.ec == std::errc()) {
+        return std::string(buf.data(), res.ptr - buf.data());
+    }
+
+    hangle_to_chars_error(res, arg);
+
+    return "";
+}
+
+static std::string ToStr(const double arg)
+{
+    std::array<char, 32> buf;
+
+    const auto res = std::to_chars(buf.data(), buf.data() + buf.size(), arg);
+
+    if (res.ec == std::errc()) {
+        return std::string(buf.data(), res.ptr - buf.data());
+    }
+
+    hangle_to_chars_error(res, arg);
+
+    return "";
+}
 
 static std::string ToStr(const double value, const int precision)
 {

utils/ephinterp.cpp

@@ -86,7 +86,7 @@ int cinterp_pvac(
         /* Position */
         if (j < 3) {
             if (fabs(ephi.outv[j + 3][0]) > 1.e-10) {
-                /* Use velocities if they exist (hermite) */
+                /* Use velocities if they exists (hermite) */
                 hermite(pindex, 2, ephi.jds, &ephi.outv[j][0], &ephi.outv[j + 3][0], ephi.nv, 10, itime, &outvec[j], &vz, ircode);
             }
             else {
@@ -95,7 +95,7 @@ int cinterp_pvac(
             }
         }
             /* Velocity */
-            /* Interpolate if they exist */
+            /* Interpolate if they exists */
         else if (fabs(ephi.outv[j][0]) > 1.e-10) {
             hermite(pindex, 1, ephi.jds, &ephi.outv[j][0], &z, ephi.nv, 10, itime, &outvec[j], &vz, ircode);
         }