parser:operator precedence tests

1 files changed, 71 insertions, 0 deletions

diff --git a/parser/parser_test.go b/parser/parser_test.go
index d3e2d1d..ddacb17 100644
--- a/parser/parser_test.go
+++ b/parser/parser_test.go
@@ -316,3 +316,74 @@ func TestParsingInfixExpressions(t *testing.T) {
 		}
 	}
 }
+
+// Operator precedence tests.
+
+func TestOperatorPrecedenceParsing(t *testing.T) {
+	tests := []struct {
+		input    string
+		expected string
+	}{
+		{
+			"-a * b",
+			"((-a) * b)",
+		},
+		{
+			"!-a",
+			"(!(-a))",
+		},
+		{
+			"a + b + c",
+			"((a + b) + c)",
+		},
+		{
+			"a + b - c",
+			"((a + b) - c)",
+		},
+		{
+			"a * b * c",
+			"((a * b) * c)",
+		},
+		{
+			"a * b / c",
+			"((a * b) / c)",
+		},
+		{
+			"a + b / c",
+			"(a + (b / c))",
+		},
+		{
+			"a + b * c + d / e - f",
+			"(((a + (b * c)) + (d / e)) - f)",
+		},
+		{
+			"3 + 4; -5 * 5",
+			"(3 + 4)((-5) * 5)",
+		},
+		{
+			"5 > 4 == 3 < 4",
+			"((5 > 4) == (3 < 4))",
+		},
+		{
+			"5 < 4 != 3 > 4",
+			"((5 < 4) != (3 > 4))",
+		},
+		{
+			"3 + 4 * 5 == 3 * 1 + 4 * 5",
+			"((3 + (4 * 5)) == ((3 * 1) + (4 * 5)))",
+		},
+	}
+
+	for _, tt := range tests {
+		var l *lexer.Lexer = lexer.New(tt.input)
+		var p *Parser = New(l)
+		var program *ast.Program = p.ParseProgram()
+		checkParserErrors(t, p)
+
+		var actual string = program.String()
+
+		if actual != tt.expected {
+			t.Errorf("expected=%q, got=%q", tt.expected, actual)
+		}
+	}
+}