interpreter

Behavioral » Interpreter

Elements

• Interpreter: the one who interpret the language;
• Language: the whole pattern we need to be interpret;

Description

The interpreter design pattern is used to solve business cases where it's useful to have a language to perform common operations. The most famous interpreter we can talk about is probably SQL.

Implementation

The implementation is trivial. In the following examples I'll show a very simple usage of interpreter. In this case we use interpreter to calculate some mathematical operations. For example the sum and the multiplication operations.

func TestSumOperator(t *testing.T) {
	sentence := "5 + 3"
	i := interpreter{}
	_ = i.of(sentence)
	if i.exec() != 8 {
		t.Error([]string{
			"La somma di 5 con 3",
			"non dovrebbe essere",
			strconv.Itoa(i.exec()),
		})
	}
}

As you can see, given a sentence like 5 + 3 parsed, it is possible to exec the string and calculate the result.

func TestMulOperator(t *testing.T) {
	sentence := "5 * 3"
	i := interpreter{}
	_ = i.of(sentence)
	if i.exec() != 15 {
		t.Error([]string{
			"Multiplication between 5 and 3",
			"shouldnt be",
			strconv.Itoa(i.exec()),
		})
	}
}