format_arg(float) now works with the desired precision

inc/format.h

@@ -3,10 +3,16 @@
 
 
 #include "parse.h"
+#include "utility.h"
 
 
 namespace detail {
 
+template<fmt_node_t fmt_node, typename T>
+constexpr void check_fmt_params() {
+    static_assert(fmt_node.length > fmt_node.precision + 1, "Insufficient length for desired precision");
+}
+
 
 template <ConstString s>
 constexpr int get_output_len() {
@@ -28,50 +34,78 @@ constexpr int get_output_len() {
 
 template <fmt_node_t fmt_node, std::integral arg_t>
 constexpr std::array<char, fmt_node.length> format_arg(arg_t arg) {
+    check_fmt_params<fmt_node, arg_t>();
+
     std::array<char, fmt_node.length> result;
 
     // TODO: See if this is possible with charconv
     for (unsigned i = 1; i <= result.size(); ++i) {
         result[result.size() - i] = arg % 10 + 48;
-        arg = arg / 10;
+        arg                       = arg / 10;
     }
 
     return result;
 }
 
 template <fmt_node_t fmt_node, std::floating_point arg_t>
-constexpr std::array<char, fmt_node.length> format_arg(arg_t) {
+constexpr std::array<char, fmt_node.length> format_arg(arg_t arg) {
+    check_fmt_params<fmt_node, arg_t>();
+
     std::array<char, fmt_node.length> result;
 
+    constexpr unsigned len_before_point =
+        fmt_node.length - fmt_node.precision - 1;
+
+    result[result.size() - fmt_node.precision - 1] = '.';
+
     // TODO: See if this is possible with charconv
-    for (auto& c : result)
-        c = 'f';
+
+    constexpr unsigned multiplier = const_pow(10, fmt_node.precision);
+    arg = arg * multiplier;
+
+    for (unsigned i = result.size()-1; i >= result.size() - fmt_node.precision; --i) {
+        result[i] = static_cast<int>(arg) % 10 + 48;
+        arg = arg / 10;
+    }
+
+    for (unsigned i = fmt_node.precision + 2; i <= result.size(); ++i) {
+        result[result.size() - i] = static_cast<int>(arg) % 10 + 48;
+        arg                       = arg / 10;
+    }
+
+    /*
+    for (unsigned i = fmt_node.precision + 1; i <= result.size(); ++i) {
+        result[result.size() - i] = static_cast<int>(arg) % 10 + 48;
+        arg                       = arg / 10;
+    }
+     */
 
     return result;
 }
 
 template <fmt_node_t fmt_node>
 constexpr std::array<char, fmt_node.length> format_arg(const char* arg) {
+    check_fmt_params<fmt_node, const char*>();
+
     std::array<char, fmt_node.length> result;
 
     for (auto& c : result) {
         if (*arg != '\0')
             c = *(arg++);
         else
-            c = '-';
+            c = '_';
     }
 
     return result;
 }
 
 template <auto t_ast, unsigned t_ast_i = 0, unsigned t_result_i = 0,
-        typename char_array_t>
+          typename char_array_t>
 constexpr char_array_t format_args(char_array_t result) {
     return result;
 }
 
 
-
 template <auto t_ast, unsigned t_ast_i = 0, unsigned t_result_i = 0,
           typename char_array_t, typename first_arg_t, typename... other_args_t>
 constexpr char_array_t format_args(char_array_t result, first_arg_t first_arg,
@@ -93,7 +127,8 @@ constexpr char_array_t format_args(char_array_t result, first_arg_t first_arg,
                       result.begin() + t_result_i);
 
             return format_args<t_ast, t_ast_i + 1,
-                               t_result_i + fmt_node.length>(result, other_args...);
+                               t_result_i + fmt_node.length>(result,
+                                                             other_args...);
         }
     }
 }

inc/utility.h

@@ -0,0 +1,19 @@
+#ifndef LOGGER_UTILITY_H
+#define LOGGER_UTILITY_H
+
+
+namespace detail {
+
+
+constexpr std::size_t const_pow(std::size_t base, std::size_t pow) {
+    if (pow == 0)
+        return 1;
+    else
+        return base * const_pow(base, pow - 1);
+}
+
+
+} // namespace detail
+
+
+#endif // LOGGER_UTILITY_H

src/main.cpp

@@ -12,7 +12,7 @@ public:
 
 
 int main() {
-    constexpr auto formatted = format<"Test: {:3.8f} {:5.5} {:05.2}">(3.4, "abc", 1234);
+    const auto formatted = format<"Test: {:8.3} {:6.3} {:05.2}">(1432.4334, "abc", 1234);
 
     for (const auto& c : formatted)
         std::cout << c;