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content/en/posts/equation_solver.md

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+---
+author: "Devoalda"
+authorEmoji: 🐺
+title: "Go - Equation Solver"
+date: 2020-07-12T11:20:23+08:00
+description: Equation Solver with Go
+draft: false
+hideToc: false
+enableToc: true
+enableTocContent: true
+tocPosition: inner
+tocLevels: ["h1", "h2", "h3"]
+tags:
+- go
+- golang
+- script
+- programming
+series:
+- Go
+categories:
+- Go
+image: images/postImages/Formula.png
+libraries:
+- mathjax
+---
+
+# Introduction
+This is a simple linear and quadratic equation solver in the terminal done in go.
+
+Equation in the form of $ax + b = cx + d$ *or*  $ax^2 + bx + c = 0$
+
+The program will first ask for type of equation, followed by getting the coefficients of each equation.
+
+# Dependencies
+* [Go](https://golang.org/dl/)
+Go Modules:
+``` Golang
+import (
+	"fmt"
+	"math"
+	"os"
+	"strconv"
+)
+```
+
+# Code
+Create a new project, and make a new file named `main.go`.
+Ensure that project path is in `$GOPATH`, this can be checked in your shell with `echo $GOPATH`
+
+## FloatToString Method
+This program uses floating points to allow for fractions and decimal numbers in the calculation. This method converts float to string
+```golang
+func FloatToString(input_num float64) string {
+	// to convert a float number to a string
+	return strconv.FormatFloat(input_num, 'f', 3, 64)
+}
+```
+This method will be used throughout the program.
+
+## Linear Equation Solver
+Equation of $ax + b = cx +d$ would be easy to solve by rearranging the function into $(a - c)x = d - b$, solving it with this equation: $$x = {d - b \over a - c}$$ Where $a \ne c$
+
+``` golang
+func linearEqn() {
+  // Declare coefficients
+	var a, b, c, d float64
+
+	fmt.Println("Linear Equation Solver")
+	fmt.Println("Eqation in the form of ax + b = cx + d ")
+
+  // Scan and check for null or empty values
+	_, err := fmt.Scan(&a, &b, &c, &d)
+	if err != nil {
+		panic(err)
+	}
+
+	if a == c && b == d {
+		fmt.Println("There are infinite solutions to this equation")
+	} else if a == c {
+		fmt.Println("This equations are parallel to each other, hence no root")
+	} else {
+		x := (d - b) / (a - c)
+		y := a*x + b
+		fmt.Println("Equation: (" + FloatToString(a) + ")x + (" + FloatToString(b) + ") = (" + FloatToString(c) + ")x + (" + FloatToString(d) + ")")
+		fmt.Println("The value of x:", x)
+		fmt.Printf("OR the line intersects at (%g,%g)\n", x, y)
+
+	}
+}
+```
+
+## Quadratic Equation Solver
+A Quadratic equation in the form of $ax^2 + bx + c = 0$, can be solved with the following equation: $$x = {-b \pm \sqrt{b^2-4ac} \over 2a}$$
+The program will first solve for the discriminant $b^2 - 4ac$ to determine the number of roots, and thereafter solve for the roots of the equation where the $discriminant \ge 0$
+
+```golang
+func quadraticEqn() {
+	var a, b, c float64
+
+	fmt.Println("Quadric Equation Solver")
+	fmt.Println("Equation in the form of ax^2+bx+c = 0")
+	fmt.Println("Where a > 0")
+	fmt.Println()
+	fmt.Println("Enter a, b, c, each in a new line:")
+
+	// Scan and check for null or empty variables
+	_, err := fmt.Scan(&a, &b, &c)
+	if err != nil {
+		panic(err)
+	}
+
+  // Panic if coefficient of x^2 <= 0
+	if a <= 0.0 {
+		panic("Coefficient of a cannot be <= 0")
+	} else {
+
+		eqn := "(" + FloatToString(a) + ")x^2 +(" + FloatToString(b) + ")x +(" + FloatToString(c) + ")"
+		fmt.Println("Equation:", eqn)
+		fmt.Println("a:", a)
+		fmt.Println("b:", b)
+		fmt.Println("c:", c)
+
+    // Solve of discriminant
+		discriminant := b*b - 4*a*c
+		fmt.Println("Discriminant:", discriminant)
+
+		if discriminant < 0 {
+			// No Real Roots
+			fmt.Println("Equation has no real roots")
+
+		} else if discriminant == 0 {
+			// 1 real root
+			alpha := (-b + math.Sqrt(discriminant)) / (2.0 * a)
+			fmt.Printf("x = %g\n", alpha)
+
+		} else {
+			//2 real roots
+			alpha := (-b + math.Sqrt(discriminant)) / (2.0 * a)
+			beta := (-b - math.Sqrt(discriminant)) / (2.0 * a)
+			fmt.Printf("x = %g or x = %g\n", alpha, beta)
+
+		}
+
+	}
+
+}
+```
+
+## Main method
+This will be the Terminal UI(TUI) to get users to choose the type of equation
+``` golang
+func main() {
+	fmt.Println("Equation Solver by Devoalda")
+	fmt.Println("Enter type of equation:")
+	fmt.Println("1. Linear Equation (ax + b = cx + d)")
+	fmt.Println("2. Quadratic Equation (ax^2 + bx + c = 0)")
+
+	//Single Variable scan
+	var choice int
+	_, err := fmt.Scanf("%d", &choice)
+	if err != nil {
+		panic(err)
+	}
+
+	//Switch case
+	switch choice {
+	case 1:
+		linearEqn()
+	case 2:
+		quadraticEqn()
+	default:
+		fmt.Println("Unrecognised choice, quitting program now!")
+		os.Exit(3)
+	}
+}
+```
+
+# Summary
+The Program can be executed with `go run main.go`. All coefficients can be integers or floats.
+
+## Full Code
+``` golang
+package main
+
+import (
+	"fmt"
+	"math"
+	"os"
+	"strconv"
+)
+
+func main() {
+	fmt.Println("Equation Solver by Devoalda")
+	fmt.Println("Enter type of equation:")
+	fmt.Println("1. Linear Equation (ax + b = cx + d)")
+	fmt.Println("2. Quadratic Equation (ax^2 + bx + c = 0)")
+
+	//Single Variable scan
+	var choice int
+	_, err := fmt.Scanf("%d", &choice)
+	if err != nil {
+		panic(err)
+	}
+
+	//Switch case
+	switch choice {
+	case 1:
+		linearEqn()
+	case 2:
+		quadraticEqn()
+	default:
+		fmt.Println("Unrecognised choice, quitting program now!")
+		os.Exit(3)
+	}
+}
+
+func linearEqn() {
+	var a, b, c, d float64
+
+	fmt.Println("Linear Equation Solver")
+	fmt.Println("Eqation in the form of ax + b = cx + d ")
+
+	_, err := fmt.Scan(&a, &b, &c, &d)
+	if err != nil {
+		panic(err)
+	}
+
+	if a == c && b == d {
+		fmt.Println("There are infinite solutions to this equation")
+	} else if a == c {
+		fmt.Println("This equations are parallel to each other, hence no root")
+	} else {
+		x := (d - b) / (a - c)
+		y := a*x + b
+		fmt.Println("Equation: (" + FloatToString(a) + ")x + (" + FloatToString(b) + ") = (" + FloatToString(c) + ")x + (" + FloatToString(d) + ")")
+		fmt.Println("The value of x:", x)
+		fmt.Printf("OR the line intersects at (%g,%g)\n", x, y)
+
+	}
+}
+
+func quadraticEqn() {
+	var a, b, c float64
+
+	fmt.Println("Quadric Equation Solver")
+	fmt.Println("Equation in the form of ax^2+bx+c = 0")
+	fmt.Println("Where a > 0")
+	fmt.Println()
+	fmt.Println("Enter a, b, c, each in a new line:")
+
+	_, err := fmt.Scan(&a, &b, &c)
+	if err != nil {
+		panic(err)
+	}
+
+	if a <= 0.0 {
+		panic("Coefficient of a cannot be <= 0")
+	} else {
+
+		eqn := "(" + FloatToString(a) + ")x^2 +(" + FloatToString(b) + ")x +(" + FloatToString(c) + ")"
+		fmt.Println("Equation:", eqn)
+		fmt.Println("a:", a)
+		fmt.Println("b:", b)
+		fmt.Println("c:", c)
+
+		discriminant := b*b - 4*a*c
+		fmt.Println("Discriminant:", discriminant)
+
+		if discriminant < 0 {
+			// No Real Roots
+			fmt.Println("Equation has no real roots")
+
+		} else if discriminant == 0 {
+			// 1 real root
+			alpha := (-b + math.Sqrt(discriminant)) / (2.0 * a)
+			fmt.Printf("x = %g\n", alpha)
+
+		} else {
+			//2 real roots
+			alpha := (-b + math.Sqrt(discriminant)) / (2.0 * a)
+			beta := (-b - math.Sqrt(discriminant)) / (2.0 * a)
+			fmt.Printf("x = %g or x = %g\n", alpha, beta)
+
+		}
+
+	}
+
+}
+
+func FloatToString(input_num float64) string {
+	// to convert a float number to a string
+	return strconv.FormatFloat(input_num, 'f', 3, 64)
+}
+```
+## Building the program
+Build the go project at the **project root** with the command `go build`
+If `$GOPATH` is in your `$PATH`, you can run the program with the program name `eqn`
+The compiled binary is located in `$GOROOT/bin/`, where you can run the program with `./eqn`
+{{< expand "Credits" >}}
+<a target="_blank" href="https://icons8.com/icons/set/formula-fx">Formula FX icon</a> icon by <a target="_blank" href="https://icons8.com">Icons8</a>
+{{< /expand >}}