add support for additional arithmetic operators

Major Changes:
* support subtraction, multiplication, division, modulo
* print syntax errors when they occur

Git issue references:

Gamelan music currently playing: Gendhing Prabu Mataram

Co-authored-by: Mouse Reeve <[email protected]>

compterpreter.go

@@ -87,12 +87,27 @@ func (c *Compterpreter) LoadSourceCode() error {
 }
 
 func (c *Compterpreter) Interpret() error {
+	var (
+		err error
+	)
+
 	// Identifies tokens in the provided .doc code
-	c.Lex()
+	err = c.Lex()
+	if err != nil {
+		return err
+	}
+
 	// Creates c.StackTree representing the provided .doc code
-	c.Parse()
+	err = c.Parse()
+	if err != nil {
+		return err
+	}
+
 	// Actually dockerize and evaluate the StackTree
-	c.Evaluate()
+	err = c.Evaluate()
+	if err != nil {
+		return err
+	}
 
 	return nil
 }

memorycell/main.go

@@ -5,6 +5,7 @@ import (
 	"io"
 	"io/ioutil"
 	"log"
+	"math"
 	"net/http"
 	"os"
 	"strconv"
@@ -91,6 +92,36 @@ func (c *Computation) ExecHandler() string {
 		input2, _ := strconv.Atoi(c.Dependencies[1])
 
 		result := strconv.Itoa(input1 + input2)
+		return result
+	case dockerlang.SUBTRACTION_OPERATOR:
+		input1, _ := strconv.Atoi(c.Dependencies[0])
+		input2, _ := strconv.Atoi(c.Dependencies[1])
+
+		result := strconv.Itoa(input1 - input2)
+		return result
+	case dockerlang.MULTIPLICATION_OPERATOR:
+		input1, _ := strconv.Atoi(c.Dependencies[0])
+		input2, _ := strconv.Atoi(c.Dependencies[1])
+
+		result := strconv.Itoa(input1 * input2)
+		return result
+	case dockerlang.DIVISION_OPERATOR:
+		input1, _ := strconv.Atoi(c.Dependencies[0])
+		input2, _ := strconv.Atoi(c.Dependencies[1])
+
+		result := strconv.Itoa(input1 / input2)
+		return result
+	case dockerlang.MODULO_OPERATOR:
+		input1, _ := strconv.ParseFloat(c.Dependencies[0], 32)
+		input2, _ := strconv.ParseFloat(c.Dependencies[1], 32)
+
+		result := strconv.FormatFloat(
+			math.Mod(input1, input2),
+			'f',
+			-1,
+			32,
+		)
+
 		return result
 	default:
 		// wtf is this type??????

parser.go

@@ -1,5 +1,7 @@
 package dockerlang
 
+import "fmt"
+
 type Stack struct {
 	Elements []AST
 }
@@ -62,6 +64,7 @@ func (c *Compterpreter) Parse() error {
 				for i := 0; i < opsExpr.Arity; i++ {
 					// make sure we're not popping nil into exprs
 					if exprStack.Peek() == nil {
+						fmt.Println("1")
 						return DockerlangSyntaxError
 					}
 					opsExpr.Operands = append([]AST{exprStack.Pop()}, opsExpr.Operands...)
@@ -80,9 +83,13 @@ func (c *Compterpreter) Parse() error {
 		return DockerlangSyntaxError
 	}
 	if opsStack.Peek() != nil {
+		fmt.Println(opsStack.Peek())
 		// oh noooo!
 		return DockerlangSyntaxError
 	}
+
+	fmt.Println(exprStack)
+
 	c.StackTree.Operands = []AST{exprStack.Pop().(*Expr)}
 
 	return nil

test/division.doc

@@ -0,0 +1 @@
+(ꙮ (‡ 99 3))

test/modulo.doc

@@ -0,0 +1 @@
+(ꙮ (% 11 2))

test/multiplication.doc

@@ -0,0 +1 @@
+(ꙮ (* 3 5))

test/nested_arithmetic.doc

@@ -0,0 +1 @@
+(ꙮ (+ († (‡ 99 3) 31) (% (* 4 11) 2)))

test/subtraction.doc

@@ -0,0 +1,2 @@
+
+(ꙮ († 5 3))