Added short form for variable definitions

src/build/Function.go

@@ -18,6 +18,7 @@ type Function struct {
 	Body      token.List
 	Variables map[string]*Variable
 	Assembler asm.Assembler
+	Error     error
 }
 
 // Compile turns a function into machine code.
@@ -27,35 +28,53 @@ func (f *Function) Compile() {
 	}
 
 	for _, line := range f.Lines() {
-		if config.Verbose {
-			fmt.Println("[line]", line)
-		}
-
 		if len(line) == 0 {
 			continue
 		}
 
-		if line[0].Kind == token.Keyword {
-			switch line[0].Text() {
-			case "let":
-				name := line[1].Text()
-				value := line[3:]
-
-				if config.Verbose {
-					fmt.Println("[variable]", name, value)
-				}
-
-				f.Variables[name] = &Variable{
-					Value:   line[3:],
-					IsConst: true,
-				}
-
-			case "return":
-				f.Assembler.Return()
-			}
+		if config.Verbose {
+			fmt.Println("[line]", line)
 		}
 
-		if line[0].Kind == token.Identifier && line[0].Text() == "syscall" {
+		err := f.compileInstruction(line)
+
+		if err != nil {
+			ansi.Red.Println(err)
+			return
+		}
+	}
+
+	f.Assembler.Return()
+}
+
+// compileInstruction compiles a single instruction.
+func (f *Function) compileInstruction(line token.List) error {
+	switch line[0].Kind {
+	case token.Keyword:
+		switch line[0].Text() {
+		case "return":
+			f.Assembler.Return()
+		}
+
+	case token.Identifier:
+		if len(line) >= 2 && line[1].Kind == token.Operator && line[1].Text() == ":=" {
+			name := line[0].Text()
+			value := line[2:]
+
+			if config.Verbose {
+				fmt.Println("[variable]", name, value)
+			}
+
+			f.Variables[name] = &Variable{
+				Value:   line[2:],
+				IsConst: true,
+			}
+
+			return nil
+		}
+
+		switch line[0].Text() {
+		case "syscall":
 			paramTokens := line[2 : len(line)-1]
 			start := 0
 			i := 0
@@ -78,7 +97,11 @@ func (f *Function) Compile() {
 				switch list[0].Kind {
 				case token.Identifier:
 					name := list[0].Text()
-					variable := f.Variables[name]
+					variable, exists := f.Variables[name]
+
+					if !exists {
+						return fmt.Errorf("Unknown identifier '%s'", name)
+					}
 
 					if !variable.IsConst {
 						panic("Not implemented yet")
@@ -101,7 +124,7 @@ func (f *Function) Compile() {
 		}
 	}
 
-	f.Assembler.Return()
+	return nil
 }
 
 // Lines returns the lines in the function body.