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.

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

Example

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

namespace zs = zollstock;

using namespace std::numbers;
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::double_t<mm>{ std::stod(argv[1]) },
            zs::double_t<mm>{ std::stod(argv[2]) },
            zs::double_t<mm>{ zs::double_t<m>{ std::stod(argv[3]) } },
        };
    }
    catch(const std::exception& e)
    {
        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 zs::double_t<g/mm3> copper_density = 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 outer_volume = outer_area * pipe_length;
    const auto inner_volume = inner_area * pipe_length;
    const auto pipe_volume = outer_volume - inner_volume;
    const zs::double_t<kg> pipe_mass = pipe_volume * copper_density;

    std::cout << std::format("pipe mass ({}): {}\n", pipe_mass.unit(), 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	—	—	—	—	—	—	—	—	—	—	—	—	✓	—	—	—	—	—	—	—	—	—	—	—	—