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execute true

What It Does

std::format() performs type-safe string formatting using replacement fields with format specifications. Format specifiers control field width, alignment, precision, and numeric base. Argument types are verified at compile time against the format string.

Why It Matters

printf() format specifiers are not type-checked, resulting in undefined behavior when specifiers mismatch argument types. std::stringstream requires explicit stream insertion operations and state management. std::format() combines type safety with a declarative format string syntax.

Example

#include <format>
#include <string>
#include <print>

int main() {
    // Basic formatting
    auto s = std::format("Hello, {}!", "world");

    // Positional arguments
    auto msg = std::format("{1} before {0}", "second", "first");

    // Format specifiers
    std::println("{:>10}", "right");    // "     right"
    std::println("{:<10}", "left");     // "left      "
    std::println("{:^10}", "center");   // "  center  "

    // Numbers
    std::println("{:08}", 42);          // "00000042"
    std::println("{:.2f}", 3.14159);    // "3.14"
    std::println("{:#x}", 255);         // "0xff"
    std::println("{:#b}", 7);           // "0b111"
}