Zollstock

A header-only type-safe zero overhead compile-time physical units C++20 library.

Zollstock is German for folding rule. It's a funny word, because it's a lie. Zoll means inch but the so called Zollstock normaly shows centimeters these days

This library increases the type-safety of your application by providing scalars associated with physical units. All additional checks are executed at compile-time, producing no overhead in your final application. The library is SI-centric. All non-SI units are defined relative to their corresponding counterpart. All built-in numeric types known in C++20 can be combined with units except char which isn't considered a number but a character. You can use signed char and unsigned char instead or better std::int8_t or std::uint8_t. There is currently no support for C++23 fixed width floating-point types. But their support is planed.

The library is still in a very early development stage. So please be careful when using it in production code.

Example

#include <zollstock/all_units.hpp>
#include <zollstock/numbers.hpp>
#include <iostream>
#include <cstdlib>
#include <format>

namespace zs = zollstock;

using namespace zs::quantities::constants;
using namespace zs::units;

[[noreturn]] void argument_error() noexcept
{
    std::cerr << "Invalid arguments\n"
              << "Usage: pcalc <wall thickness (mm)> <outer diameter (mm)> <length (m)>\n";

    std::exit(1);
}

[[nodiscard]] auto read_args(int argc, char** argv) noexcept
{
    if (argc != 4)
        argument_error();

    try
    {
        return std::tuple{
            zs::stod<mm>(argv[1]),
            zs::stod<mm>(argv[2]),
            zs::in<mm>(zs::stod<m>(argv[3])),
        };
    }
    catch(const std::exception&)
    {
        argument_error();
    }
}

int main(int argc, char** argv)
{
    // Checking arguments
    const auto [wall_thickness, outer_diameter, pipe_length] = read_args(argc, argv);

    // Calculating mass of a copper pipe
    static constexpr auto copper_density = zs::in<g/mm3>(8.1_g/cm3);
    const auto outer_radius = outer_diameter / 2;
    const auto inner_radius = outer_radius - wall_thickness;
    const auto outer_area = pi * outer_radius * outer_radius;
    const auto inner_area = pi * inner_radius * inner_radius;
    const auto ring_area = outer_area - inner_area;
    const auto pipe_volume = ring_area * pipe_length;
    const auto pipe_mass = zs::in<kg>(pipe_volume * copper_density);

    std::cout << std::format("pipe mass: {}\n", pipe_mass);

    return 0;
}

Supported SI base units

prefix	Q	R	Y	Z	E	P	T	G	M	k	h	da		d	c	m	μ	n	p	f	a	z	y	r	q
s	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓
m	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓
g	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓
A
K	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓
mol
cd

Supported SI named derived units

prefix	Q	R	Y	Z	E	P	T	G	M	k	h	da		d	c	m	μ	n	p	f	a	z	y	r	q
rad	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓
sr
Hz
N
Pa
J
W
C
V
F
Ω (ohm)
S
Wb
T
°C (degc)
lm
lx
Bq
Gy
Sv
kat

SI unnamed derived units with special support

There is no finite set of unamed derived units. You can combine base units as you like. But there are some unamed derived units with predefined symbols and literals. These symbols and literals are not required. Their only purpose is to increase readability.

prefix	Q	R	Y	Z	E	P	T	G	M	k	h	da		d	c	m	μ	n	p	f	a	z	y	r	q
m² (m2)	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓
m³ (m3)	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓
s² (s2)	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓

Supported Non-SI units

prefix	Q	R	Y	Z	E	P	T	G	M	k	h	da		d	c	m	μ	n	p	f	a	z	y	r	q
asec	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓
gon	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓
° (deg)	—	—	—	—	—	—	—	—	—	—	—	—	✓	—	—	—	—	—	—	—	—	—	—	—	—
amin	—	—	—	—	—	—	—	—	—	—	—	—	✓	—	—	—	—	—	—	—	—	—	—	—	—
min	—	—	—	—	—	—	—	—	—	—	—	—	✓	—	—	—	—	—	—	—	—	—	—	—	—
h	—	—	—	—	—	—	—	—	—	—	—	—	✓	—	—	—	—	—	—	—	—	—	—	—	—
d	—	—	—	—	—	—	—	—	—	—	—	—	✓	—	—	—	—	—	—	—	—	—	—	—	—
a	—	—	—	—	—	—	—	—	—	—	—	—	✓	—	—	—	—	—	—	—	—	—	—	—	—