[Feat] CLI

README.md

@@ -10,6 +10,12 @@ $ go get -u github.com/nyttikord/gomath@latest
 ```
 You can replace `latest` with any valid tags.
 
+You can install a CLI with
+```bash
+$ go install github.com/nyttikord/gomath/cmd@latest
+```
+You can replace `latest` with any valid tags.
+
 ### Calculate
 
 To parse an expression and calculate it, use `gomath.ParseAndCalculate(string, *gomath.Options) (string, error)`.
@@ -38,6 +44,14 @@ err == nil // true
 res == `\frac{1 + \frac{2}{3}}{2}` // true
 ```
 
+### CLI
+
+You can get the help with `gomath help`.
+
+To evaluate an expression, use `gomath eval <expression>`.
+
+To convert to $\LaTeX$ an expression, use `gomath latex <expression>`. 
+
 ### Special case
 
 The written representation of calculation is definitely not compatible with computers.

cmd/main.go

@@ -0,0 +1,50 @@
+package main
+
+import (
+	"fmt"
+	"github.com/nyttikord/gomath"
+	"os"
+	"strings"
+)
+
+func main() {
+	if len(os.Args) < 2 {
+		fmt.Printf("Usage: %s <subcommand>\nUse %s help to get the help.\n", os.Args[0], os.Args[0])
+		os.Exit(1)
+	}
+	subcommand := os.Args[1]
+	switch subcommand {
+	case "help":
+		if len(os.Args) != 2 {
+			fmt.Printf("Help does not take any arguments.\n")
+			os.Exit(1)
+		}
+		fmt.Printf("Subcommands:\n- eval <expression> -> evaluate an expression.\n- latex <expression> -> latexify an expression.\n")
+	case "eval":
+		if len(os.Args) < 3 {
+			fmt.Printf("Usage: %s eval <expression>.\n", os.Args[0])
+			os.Exit(1)
+		}
+		expression := strings.Join(os.Args[2:], " ")
+		res, err := gomath.Parse(expression)
+		if err != nil {
+			fmt.Println(err)
+			os.Exit(2)
+		}
+		fmt.Println(res)
+	case "latex":
+		if len(os.Args) < 3 {
+			fmt.Printf("Usage: %s latex <expression>.\n", os.Args[0])
+			os.Exit(1)
+		}
+		expression := strings.Join(os.Args[2:], " ")
+		res, err := gomath.ParseAndConvertToLaTeX(expression, nil)
+		if err != nil {
+			fmt.Println(err)
+			os.Exit(2)
+		}
+		fmt.Println(res)
+	default:
+		fmt.Printf("Unknown subcommand: %s\nUse %s help to get the help.\n", subcommand, os.Args[0])
+	}
+}