Added contains operator.

README.md

@@ -6,25 +6,14 @@ This library enables query against JSON. Currently supported operators are: (pre
 ```
 ||
 &&
-= != > < >= <= ~= !~= is isnot
+= != > < >= <= ~= !~= is isnot contains
 + -
 * / %
 ^
 ( )
 ```
 
-## Changes
-
-The following operators are added: (Credit goes to Ahmad Baitalmal)
-* is defined
-* isnot defined
-* is null
-* isnot null
-
-Previously I was hoping to make the query as similar to SQL `WHERE` clause as possible. Later I found a problem parsing the term `PRIORITY>5`. The tokenizer split it as `PRI`, `OR`, `ITY`, `>`, `5`, since `OR` was then an operator, which is terribly wrong. At that point, I thought of two choices:				
-1. to force the query expression to contain at least one white space between tokens, thus `PRIORITY>5` should be written as `PRIORITY > 5`;		
-2. to replace operators as follows:		
-
+The following are the operators maping to SQL:
 * `AND` to `&&`
 * `OR`	to `||`
 * `RLIKE` to `~=`
@@ -127,6 +116,9 @@ func main() {
 	// [map[hobby:<nil> skills:[IC Electric design Verification] name:enny gender:f age:36]] <nil>
 
 	fmt.Println(parser.Query("hobby isnot null"))
-	// [map[name:sam gender:m age:1 hobby:dancing skills:[Eating Sleeping Crawling]]] <nil>
+  // [map[name:sam gender:m age:1 hobby:dancing skills:[Eating Sleeping Crawling]]] <nil>
+
+  fmt.Println(parser.Query("skills contains 'Eating'"))
+  // [map[age:1 gender:m hobby:dancing name:sam skills:[Eating Sleeping Crawling]]] <nil>
 }
 ```

exparser_test.go

@@ -18,6 +18,7 @@ func TestTokenize(t *testing.T) {
 		{"'123  456' 789", []string{"'123  456'", "789"}},
 		{`123 "456  789"`, []string{"123", "\"456  789\""}},
 		{`123 "456  '''789"`, []string{"123", "\"456  '''789\""}},
+		{`2*x+y is null`, []string{"2", "*", "x", "+", "y", "is", "null"}},
 	}
 	var fail = []struct {
 		in string

jsonql_test.go

@@ -45,11 +45,11 @@ func TestParse(t *testing.T) {
 
 	var pass = []struct {
 		in string
-		ex int
 	}{
-		{"name='elgs'", 1},
-		{"gender='f'", 1},
-		{"skills.[1]='Sleeping'", 1},
+		{"name='elgs'"},
+		{"gender='f'"},
+		{"skills.[1]='Sleeping'"},
+		{"skills contains 'Verification'"},
 	}
 	var fail = []struct {
 		in string

sql_operators.go

@@ -110,6 +110,27 @@ var sqlOperators = map[string]*Operator{
 			return "false", nil
 		},
 	},
+	"contains": {
+		Precedence: 5,
+		Eval: func(symbolTable interface{}, left string, right string) (string, error) {
+			l, err := evalToken(symbolTable, left)
+			if err != nil {
+				return "false", err
+			}
+			r, err := evalToken(symbolTable, right)
+			if err != nil {
+				return "false", err
+			}
+			if al, ok := l.([]interface{}); ok {
+				for _, item := range al {
+					if item == r {
+						return "true", nil
+					}
+				}
+			}
+			return "false", nil
+		},
+	},
 	"=": {
 		Precedence: 5,
 		Eval: func(symbolTable interface{}, left string, right string) (string, error) {