Implemented block instruction parsing

src/build/token/Keywords.go

@@ -3,4 +3,5 @@ package token
 // Keywords defines the keywords used in the language.
 var Keywords = map[string]bool{
 	"return": true,
+	"loop":   true,
 }

src/build/token/List.go

@@ -7,6 +7,28 @@ import (
 // List is a slice of tokens.
 type List []Token
 
+// IndexKind returns the position of a token kind within a token list.
+func (list List) IndexKind(kind Kind) int {
+	for i, token := range list {
+		if token.Kind == kind {
+			return i
+		}
+	}
+
+	return -1
+}
+
+// LastIndexKind returns the position of the last token kind within a token list.
+func (list List) LastIndexKind(kind Kind) int {
+	for i := len(list) - 1; i >= 0; i-- {
+		if list[i].Kind == kind {
+			return i
+		}
+	}
+
+	return -1
+}
+
 // String implements string serialization.
 func (list List) String() string {
 	builder := bytes.Buffer{}

src/build/token/Token.go

@@ -11,8 +11,8 @@ type Token struct {
 	Bytes    []byte
 }
 
-// After returns the position after the token.
-func (t *Token) After() int {
+// End returns the position after the token.
+func (t *Token) End() int {
 	return t.Position + len(t.Bytes)
 }