README.md

@@ -5,7 +5,7 @@
 * Convert any integral type to a string at compile-time
 * Supports converting to any base between 2 and 36 inclusive
 * No external dependencies, only includes `type_traits` for template parameter checking
-* Works best in C++20 GCC or C++17/20 Clang
+* Supports custom character types, e.g. `to_string<123, 10, wchar_t>`
 
 **How to use:**
 
@@ -22,31 +22,31 @@ With `to_string`, all that will be found in program disassembly are the resultin
 
 Try it [on Compiler Explorer](https://godbolt.org/z/T-MFoh).
 
-**Known issues:**
-
-* With C++17 GCC, `to_string` must be used to initialize variables; otherwise, the integer-string conversion is done at run-time.
-
 # How it works
 
 The basic structure of `to_string` is shown below:
 
 ```cpp
-template<auto N, unsigned int base, /* N type-check and base bounds-check */>
+template<auto N, unsigned int base, typename char_type, /* N type-check and base bounds-check */>
 struct to_string_t {
-    char buf[];                          // Size selection explained later.
+    char_type buf[];                          // Size selection explained later.
     constexpr to_string_t() {}                // Converts the integer to a string stored in buf.
-    constexpr operator char *() {}       // These allow for the object to be implicitly converted
+    constexpr operator char_type *() {}       // These allow for the object to be implicitly converted
-    constexpr operator const char *() {} // to a character pointer.
+    constexpr operator const char_type *() {} // to a character pointer.
+    
+    // begin() and end() are supported too.
 };
 
-template<auto N, unsigned int base = 10>
+template<auto N, unsigned int base = 10, typename char_type = char>
-to_string_t<N, base> to_string;          // Simplifies usage: to_string_t<N, base>() becomes to_string<N, base>.
+constexpr to_string_t<N, base, char_type> to_string;    // Simplifies usage, e.g. to_string_t<367>() becomes to_string<367>.
 ```
 
 Since the number and base are template parameters, each differing `to_string` use will get its own character buffer.
 
 The integer/string conversion is done using a simple method I learned over the years, where the string is built in reverse using `n % base` to calculate the value of the lowest digit:
 
+(*Note: The below examples of code are not up-to-date, though they still give a general idea of how `to_string` works.*)
+
 ```cpp
 constexpr to_string_t() {
     auto ptr = buf + sizeof(buf) / sizeof(buf[0]);

to_string.hpp

@@ -15,49 +15,60 @@
  * @tparam N Number to convert
  * @tparam base Desired base, can be from 2 to 36
  */
-template<auto N, unsigned int base,
+template<auto N, unsigned int base, typename char_type,
     std::enable_if_t<std::is_integral_v<decltype(N)>, int> = 0,
     std::enable_if_t<(base > 1 && base < 37), int> = 0>
-struct to_string_t {
+class to_string_t {
     // The lambda calculates what the string length of N will be, so that `buf`
     // fits to the number perfectly.
-    char buf[([] {
+    char_type buf[([]() constexpr noexcept {
-                  unsigned int len = N >= 0 ? 1 : 2;
+                       unsigned int len = N > 0 ? 1 : 2;
                        for (auto n = N; n; len++, n /= base);
                        return len;
-             }())];
+                   }())] = {};
 
+ public:
     /**
      * Constructs the object, filling `buf` with the string representation of N.
      */
-    constexpr to_string_t() {
+    constexpr to_string_t() noexcept {
-        auto ptr = buf + sizeof(buf) / sizeof(buf[0]);
+        auto ptr = end();
         *--ptr = '\0';
-        for (auto n = N; n; n /= base)
+        if (N != 0) {
+            for (auto n = N < 0 ? -N : N; n; n /= base)
                 *--ptr = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"[(N < 0 ? -1 : 1) * (n % base)];
             if (N < 0)
                 *--ptr = '-';
+        } else {
+            buf[0] = '0';
+        }
     }
 
-    /**
+    // Support implicit casting to `char *` or `const char *`.
-     * Allows implicit conversion of this object to a `char *`.
+    constexpr operator char_type *() noexcept { return buf; }
-     */
+    constexpr operator const char_type *() const noexcept { return buf; }
-    constexpr operator char *() {
-        return buf;
-    }
 
-    /**
+    constexpr auto size() const noexcept { return sizeof(buf) / sizeof(buf[0]); }
-     * Allows implicit conversion of this object to a `const char *`.
+    // Element access
-     */
+    constexpr auto data() noexcept { return buf; }
-    constexpr operator const char *() const {
+    constexpr const auto data() const noexcept { return buf; }
-        return buf;
+    constexpr auto& operator[](unsigned int i) noexcept { return buf[i]; }
-    }
+    constexpr const auto& operator[](unsigned int i) const noexcept { return buf[i]; }
+    constexpr auto& front() noexcept { return buf[0]; }
+    constexpr const auto& front() const noexcept { return buf[0]; }
+    constexpr auto& back() noexcept { return buf[size() - 1]; }
+    constexpr const auto& back() const noexcept { return buf[size() - 1]; }
+    // Iterators
+    constexpr auto begin() noexcept { return buf; }
+    constexpr const auto begin() const noexcept { return buf; }
+    constexpr auto end() noexcept { return buf + size(); }
+    constexpr const auto end() const noexcept { return buf + size(); }
 };
 
 /**
  * Simplifies use of `to_string_t` from `to_string_t<N>()` to `to_string<N>`.
  */
-template<auto N, unsigned int base = 10>
+template<auto N, unsigned int base = 10, typename char_type = char>
-to_string_t<N, base> to_string;
+constexpr to_string_t<N, base, char_type> to_string;
 
 #endif // TCSULLIVAN_TO_STRING_HPP_