egladysh / metamath

Meta mathematics. Symbolic functions and derivatives.

metamath

Meta mathematic

metamath is a tiny header-only library. It can be used for symbolic computations on single-variable functions, such as dynamic computations of derivatives. The operator precedence rules are naturally handled by the compiler. The library could be useful for building custom DSL's in C++.

func.h contains definitions for some of the cmath functions: Sin/Cos, Ln, Pow, Abs, Sqrt, Exp, more to come... Arithmetic operations with functions are supported:

auto f1 = 3 * x;
auto f2 = Ln(x);
auto f = f1 + f2;

auto y1 = f(2);
auto y2 = f(4);

as well as function composition:

auto f = Ln(x);
auto g = 3 * x;
auto h = f(g);

auto y1 = h(2);

Examples of Functions and Derivatives

Example:

using namespace metamath;

auto f = 3 * x * x;

std::cout << "f(x) = " << f << std::endl;
std::cout << "f(4) = " << f(4.f) << std::endl;
std::cout << "------" << std::endl;

// take derivative
auto df = derivative(f);
std::cout << "f`(x) = " << df << std::endl;
std::cout << "f`(4) = " << df(4.f) << std::endl;

This will produce the following output:

f(x) = 3 * x * x
f(4) = 48
------
f`(x) = ((0 * x + 3) * x + 3 * x)
f`(4) = 24

Example:

auto f =  4 * Sin(2 * x);

std::cout << "f(x) = " << f << std::endl;
std::cout << "f(pi) = " << f(M_PI) << std::endl;
std::cout << "f(pi/4) = " << f(M_PI/4.f) << std::endl;
std::cout << "------" << std::endl;

//take derivative
auto df = derivative(f);
std::cout << "f`(x) = " << df << std::endl;
std::cout << "f`(pi) = " << df(M_PI) << std::endl;
std::cout << "f`(pi/4) = " << df(M_PI/4.f) << std::endl;

This will produce the following output:

f(x) = 4 * sin(2 * x)
f(pi) = 6.99382e-07
f(pi/4) = 4
------
f`(x) = (0 * sin(2 * x) + 4 * cos(2 * x) * (0 * x + 2))
f`(pi) = 8
f`(pi/4) = -3.49691e-07

Build

Requirements

C++14 or later

Steps to build the sample

• Suppose you cloned to [HOME]/work/metamath

• For out-of-source, create a build folder in [HOME]/work, and go there.

    $mkdir build
    $cd build
  

• Run cmake

    $cmake ../metamath
  

• Build it

    $make
  

• You can now run a sample (the sample source is in metamath/sample/)

    $./sample/mms
  

• The sample output:

    Metamath sample
    ======
    f(x) = 3 * x * x
    f(4) = 48
    ------
    f`(x) = ((0 * x + 3) * x + 3 * x)
    f`(4) = 24
    ======
  
    ======
    f(x) = 3 * x
    f(2) = 6
    f(3) = 9
    ------
    f`(x) = (0 * x + 3)
    f`(2) = 3
    ======
  
    ======
    f(x) = ((1) / (x))
    f(2) = 0.5
    f(3) = 0.333333
    ------
    f`(x) = (((0 * x - 1)) / (x * x))
    f`(2.f) = -0.25
    ======
  
    ======
    f(x) = ((2 * (x + 1)) / (x))
    f(2) = 3
    f(3) = 2.66667
    ------
    f`(x) = ((((0 * (x + 1) + 2 * 1) * x - 2 * (x + 1))) / (x * x))
    f`(2) = -0.5
    ======
  
    ======
    f(x) = 4 * sin(2 * x)
    f(pi) = 6.99382e-07
    f(pi/4) = 4
    ------
    f`(x) = (0 * sin(2 * x) + 4 * cos(2 * x) * (0 * x + 2))
    f`(pi) = 8
    f`(pi/4) = -3.49691e-07
    ======
  
    ======
    f(x) = sqrt(x)
    f(4) = 2
    f(6) = 2.44949
    ------
    f`(x) = ((1) / (2 * sqrt(x)))
    f`(4) = 0.25
    f`(6) = 0.204124
    ======
  
    ======
    f(x) = (3 * x^2)
    f(4) = 144
    f(6) = 324
    ------
    f`(x) = 2 * (3 * x^1) * (0 * x + 3)
    f`(4) = 72
    f`(6) = 108
    ======
  
    ======
    f(x) = e^(3 * x)
    f(4) = 162755
    f(6) = 6.566e+07
    ------
    f`(x) = e^(3 * x) * (0 * x + 3)
    f`(4) = 488264
    f`(6) = 1.9698e+08
    ======
  
    ======
    f(x) = ln(3 * x)
    f(4) = 2.48491
    f(6) = 2.89037
    ------
    f`(x) = ((1) / (3 * x)) * (0 * x + 3)
    f`(4) = 0.25
    f`(6) = 0.166667
    ======
  
    ======
    f(x) = |3 * x|
    f(-4) = 12
    f(6) = 18
    ------
    f`(x) = ((3 * x) / (|3 * x|)) * (0 * x + 3)
    f`(-4) = -3
    f`(6) = 3
    ======
  
    ======
    f(x) = ln(x)
    g(x) = 3 * x
    h(x) = f(g(x)) = ln(3 * x)
    h(4) = 2.48491
    ------
    h`(x) = ((1) / (3 * x)) * (0 * x + 3)
    h`(4) = 0.25
    ======