Done with the book! Added hash maps and the puts builtin.

Signed-off-by: jmug <u.g.a.mariano@gmail.com>

pkg/ast/hash.go

@@ -0,0 +1,24 @@
+package ast
+
+import (
+	"strings"
+
+	"code.jmug.me/jmug/interpreter-in-go/pkg/token"
+)
+
+type HashLiteral struct {
+	Token token.Token // The "{" token
+	Pairs map[Expression]Expression
+}
+
+func (hl *HashLiteral) expressionNode() {}
+func (hl *HashLiteral) TokenLiteral() string {
+	return hl.Token.Literal
+}
+func (hl *HashLiteral) String() string {
+	pairs := []string{}
+	for k, v := range hl.Pairs {
+		pairs = append(pairs, k.String()+":"+v.String())
+	}
+	return "{" + strings.Join(pairs, ", ") + "}"
+}