Add all the files from the interpreter repo

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

pkg/parser/precedence.go

@@ -0,0 +1,44 @@
+package parser
+
+import (
+	"code.jmug.me/jmug/interpreter-in-go/pkg/token"
+)
+
+const (
+	_ int = iota
+	LOWEST
+	EQUALS      // ==
+	LESSGREATER // > or <
+	SUM         // +
+	PRODUCT     // *
+	PREFIX      // -X or !X
+	CALL        // myFunction(X)
+	INDEX       // array[index]
+)
+
+var precedences = map[token.TokenType]int{
+	token.EQ:       EQUALS,
+	token.NOT_EQ:   EQUALS,
+	token.GT:       LESSGREATER,
+	token.LT:       LESSGREATER,
+	token.PLUS:     SUM,
+	token.MINUS:    SUM,
+	token.ASTERISK: PRODUCT,
+	token.SLASH:    PRODUCT,
+	token.LPAREN:   CALL,
+	token.LBRACKET: INDEX,
+}
+
+func (p *Parser) peekPrecedence() int {
+	if pr, ok := precedences[p.peekToken.Type]; ok {
+		return pr
+	}
+	return LOWEST
+}
+
+func (p *Parser) curPrecedence() int {
+	if pr, ok := precedences[p.curToken.Type]; ok {
+		return pr
+	}
+	return LOWEST
+}