🪡 hybstr — Hybrid Compile-Time & Runtime String Library

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Overview

hybstr provides a hybrid string type (hybstr::string_impl) that seamlessly bridges compile-time (constexpr) and runtime string handling.

Unlike std::string (purely runtime) or std::string_view (non-owning), hybstr::string_impl owns its data and can operate in both environments.

In both compile-time and runtime enviroments, all data lives in a fixed buffer known to the compiler.

hybstr lets you treat strings as first-class compile-time objects — useful for metaprogramming, code generation, embedded DSLs, or constexpr evaluation — while still functioning as a normal string type at runtime.

Features

• Hybrid compile-time / runtime Works in both constexpr and regular runtime expressions.
• Concatenation and modification Supports operations like +, append, push_back, and set<N>() in both compile time and runtime.
• NTTP Can be used as a Non-Type Template Parameter (NTTP) in C++20 and above.

Examples

Construction

#include "hybstr.hpp"
using namespace hybstr;
 
// compile time
constexpr auto s1 = string("Hello");
constexpr auto s2 = string("World");
constexpr auto s3 = s1 + ", " + s2 + "!";
 
static_assert(s3 == string("Hello, World!"));

Literals

using namespace hybstr::literals;
 
constexpr auto greet = "Hi"_hyb + ", "_hyb + "there"_hyb;
static_assert(greet == hybstr::string("Hi, there"));

From Runtime Inputs

std::string name;
std::cin >> name;
 
constexpr auto s1 = string("Hello");
 
auto msg = s1 + name;
std::cout << msg.str() << '\n'; // outupt str
std::cout << msg.view() << '\n'; // output view

Compile time utils

C++20

constexpr auto s = hybstr::string("CompileTimeText");
constexpr auto fitted = hybstr::fit_string<s>();
static_assert(fitted.capacity() == fitted.size());
 
// Or combine them if s have a big capacity with little size, this removes the extra memory at compile time
constexpr auto fitted2 = hybstr::fit_string<hybstr::string<100000>("CompileTimeText")>();

C++17 fallback macro

constexpr auto s = hybstr::string("CompileTimeText");
constexpr auto fitted = HYBSTR_FIT_STRING(s);
static_assert(fitted.capacity() == fitted.size());
 
// Or combine them if s have a big capacity with little size, this removes the extra memory at compile time
constexpr auto fitted2 = HYBSTR_FIT_STRING(hybstr::string<100000>("CompileTimeText"));

Comparison Operators

hybstr::string_impl supports all standard comparison operations:

constexpr auto a = hybstr::string("abc");
constexpr auto b = hybstr::string("abd");
 
static_assert(a < b);
static_assert(a != b);

Factory Functions

Function	Description
string()	Create an empty string.
string(const char(&)[N])	From string literal.
string(std::string_view)	From string view.
string(_Iter start, _Iter end)	From iterator range.

Mixed Usage

#include "hybstr.hpp"
#include <iostream>
 
using namespace hybstr;
 
int main() {
    constexpr auto prefix = string("Hello, ");
    std::string name;
    std::cin >> name;
 
    // Mix compile-time and runtime strings
    auto result = prefix + string(name.begin(), name.end()) + "!";
    std::cout << result.view() << '\n';
}