rpopplewell / calculus

The original Golang library for single variable differentiation and integration.

Go Calculus

A golang library supporting definite integration and differentiation of real valued, single variable, elementary and non-elementary functions.

Usage

~$ go get github.com/TheDemx27/calculus

package main

import (
  "fmt"
  "math"
  clc "github.com/rpopplewell/calculus"
)

func main() {
  // Create a new function.
  f := clc.NewFunc("1/(x^2+1)")

  // Integrate from 0 to 20.
  fmt.Println(f.AntiDiff(0, 20))

  // Differentiate at point Pi/2.
  fmt.Println(f.Diff(math.Pi/2))
}

Alternatively, you can define any function that takes and returns a float64, (i.e. a function of the form type usrFunction func(float64) float64), and then perform calculus on it. This allows you to do calculus on practically any mapping.

func fn(x float64) float64 {
  return 2*math.Floor(x)
}

func main() {
  clc.AntiDiff(fn, 0, 10)
  clc.Diff(fn, 0.5)
}

In all cases, adding an additional int argument will specify how many samples you want to use. You can also evaluate the function at a certain point using f.Eval(), and return the expression defining the function using f.Name(), e.g.

  fmt.Printf("The value of %s when x = 20 is %g\n", f.Name(), f.Eval(20))

TODO

* Gaussian Quadrature ✓ * Implement Risch Algorithm * Implement Symbolic Differentiation Patterns