Ring/Lessons/Reflection and Meta-programming

Reflection and Meta-programming Since the Ring programming language is a dynamic language, we can get answers about the program code and we can modify our code during the runtime. In this chapter we will learn about this and the available functions to use. locals() Function We can get a list of variables names in the current scope using the locals() function. Syntax: locals() --> a list contains the variables names in the current scope Example: test("hello") func test cMsg see cMsg + nl x = 10 y = 20 z = 30 see locals() Output: hello cmsg x y z globals() Function We can get a list of variables names in the global scope using the globals() function. Syntax: globals() --> a list contains variables names in the global scope Example: x=10 y=20 z=30 test() func test see "message from test()" + nl + "Global Variables:" + nl see globals() Output: message from test() Global Variables: x y z functions() Function We can get a list of functions names written in the Ring language using the functions() function. Syntax: functions() --> a list contains functions names Example: see functions() func f1 see "f1" + nl func f2 see "f2" + nl func f3 see "f3" + nl Output: f1 f2 f3 cfunctions() Function We can get a list of functions names written in the C language using the cfunctions() function. Syntax: cfunctions() --> a list contains functions names Example: aList = cfunctions() See "Count : " + len(aList) + nl for x in aList see x + "()" + nl next Output: Count : 186 len() add() del() get() clock() ... .. note:: The complete list is removed from the previous output. islocal() Function We can check if a variable is defined in the local scope or not using the islocal() function. Syntax: islocal(cVariableName) --> returns 1 if the variable is defined in the local scope returns 0 if the variable is not defined in the local scope Example: test() func test x=10 y=20 see islocal("x") + nl + islocal("y") + nl + islocal("z") + nl Output: 1 1 0 isglobal() Function We can check if a variable is defined in the global scope or not using the isglobal() function. Syntax: isglobal(cVariableName) --> returns 1 if the variable is defined in the global scope returns 0 if the variable is not defined in the global scope Example: x=10 y=20 test() func test see isglobal("x") + nl + isglobal("y") + nl + isglobal("z") + nl Output: 1 1 0 isfunction() Function We can check if a Ring function is defined or not using the isfunction() function. Syntax: isfunction(cFunctionName) --> returns 1 if the Ring function is defined returns 0 if the Ring function is not defined Example: see isfunction("f1") + nl + isfunction("f2") + nl + isfunction("f3") + nl func f1 see "message from f1()" + nl func f2 see "message from f2()" + nl Output: 1 1 0 iscfunction() Function We can check if a C function is defined or not using the iscfunction() function. Syntax: iscfunction(cFunctionName) --> returns 1 if the C function is defined returns 0 if the C function is not defined Example: see iscfunction("len") + nl + iscfunction("test") + nl Output: 1 1 0 packages() Function We can get a list of packages names using the packages() function. Syntax: packages() --> a list contains packages names Example: See packages() Package Package1 Class class1 Func f1 Package Package2 Class class1 Func f1 Package Package3 Class class1 Func f1 Package Package4 Class class1 Func f1 Output: package1 package2 package3 package4 ispackage() Function We can check if a package is defined or not using the ispackage() function. Syntax: ispackage(cPackageName) --> returns 1 if the Package is defined returns 0 if the Package is not defined Example: See ispackage("package1") + nl + ispackage("package4") + nl + ispackage("package5") + nl + ispackage("package3") + nl Package Package1 Class class1 Func f1 Package Package2 Class class1 Func f1 Package Package3 Class class1 Func f1 Package Package4 Class class1 Func f1 Output: 1 1 0 1 classes() Function We can get a list of classes names using the classes() function. Syntax: classes() --> a list contains classes names Example: See classes() Class class1 Func f1 Class class2 Func f1 Class class3 Func f1 Output: class1 class2 class3 isclass() Function We can check if a class is defined or not using the isclass() function. Syntax: isclass(cClassName) --> returns 1 if the Class is defined returns 0 if the Class is not defined Example: see isclass("class4") + nl + isclass("class3") + nl + isclass("class2") + nl Class class1 func f1 class class2 func f1 class class3 func f1 Output: 0 1 1 packageclasses() Function We can get a list of classes names inside a package using the packageclasses() function. Syntax: packageclasses(cPackageName) --> a list contains classes names inside the package Example: see "classes in Package1" + nl see packageclasses("Package1") see "classes in Package2" + nl see packageclasses("Package2") Package Package1 Class class1 Func f1 Package Package2 Class class1 Func f1 Class class2 Func f1 Class class3 func f1 Output: classes in Package1 class1 classes in Package2 class1 class2 class3 ispackageclass() Function We can check if a class is defined inside package or not using the ispackageclass() function. Syntax: ispackageclass(cPackageName,cClassName) --> returns 1 if the Class is defined returns 0 if the Class is not defined Example: see ispackageclass("package1","class1") + nl + ispackageclass("package1","class2") + nl + ispackageclass("package2","class1") + nl + ispackageclass("package2","class2") + nl Package Package1 Class class1 Func f1 Package Package2 Class class1 Func f1 Class class2 Func f1 Class class3 func f1 Output: 1 0 1 1 classname() Function We can know the class name of an object using the classname() function Syntax: classname(object) --> Returns the object class name Example: o1 = new point o2 = new rect see classname(o1) + nl # print point see classname(o2) + nl # print rect class point class rect objectid() Function We can know the object id using the objectid() function Syntax: objectid(object) --> Returns the object id Example: o1 = new point see objectid(o1) + nl test(o1) func test v see objectid(v) + nl Class point x y z Output: 021B5808 021B5808 We can check the variable to know if it's an object or not using the isobject() function Syntax: isobject(variable) --> Returns True if it's an object, False if it's not attributes() Function We can get the object attributes using the attributes() function Syntax: attributes(object) --> Returns a list contains the object attributes Example: o1 = new point aList = attributes(o1) # we can use see attributes(o1) for t in aList see t next # print xyz Class Point x y z We can get the object methods using the methods() function Syntax: methods(object) --> Returns a list contains the object methods Example: o1 = new test aList = methods(o1) for x in aList cCode = "o1."+x+"()" eval(cCode) next Class Test func f1 see "hello from f1" + nl func f2 see "hello from f2" + nl func f3 see "hello from f3" + nl func f4 see "hello from f4" + nl Output: hello from f1 hello from f2 hello from f3 hello from f4 isattribute() Function We can test if the object contains an attribute or not using the isattribute() function Syntax: isattribute(object,cAttributeName) --> Returns True if the object contains the attribute Example: o1 = new point see isattribute(o1,"x") + nl # print 1 see isattribute(o1,"t") + nl # print 0 see isattribute(o1,"y") + nl # print 1 see isattribute(o1,"z") + nl # print 1 class point x y z isprivateattribute() Function We can test if the object contains a private attribute or not using the isprivateattribute() function Syntax: isprivateattribute(object,cAttributeName) --> Returns True if the object contains the private attribute Example: o1 = new person see isprivateattribute(o1,"name") + nl + isprivateattribute(o1,"address") + nl + isprivateattribute(o1,"phone") + nl + isprivateattribute(o1,"job") + nl + isprivateattribute(o1,"salary") Class Person name address phone private job salary Output: 0 0 0 1 1 ismethod() Function We can test if the object class contains a method or not using the ismethod() function Syntax: ismethod(object,cMethodName) --> Returns True if the object class contains the method Example: o1 = new point see ismethod(o1,"print") + nl # print 1 mylist = [] mylist + new point see ismethod(mylist[1],"print") + nl # print 1 class point x y z func print see x + nl + y + nl + z + nl isprivatemethod() Function We can test if the object class contains a private method or not using the isprivatemethod() function Syntax: isprivatemethod(object,cMethodName) --> Returns True if the object class contains the private method Example: o1 = new Test see isprivatemethod(o1,"f1") + nl + isprivatemethod(o1,"f2") Class Test func f1 see "message from f1()" + nl private func f2 see "message from f2()" + nl Output: 0 1 addattribute() Function We can add an attribute (or a group of attributes) to the object state (not the class) using the addattribute() function Syntax: AddAttribute(object,cAttributeName|aAttributesList) Example(1): see new point {x=10 y=20 z=30} Class Point AddAttribute(self,["x","y","z"]) Example(2): o1 = new point addattribute(o1,"x") addattribute(o1,"y") addattribute(o1,"z") see o1 {x=10 y=20 z=30} class point Output: x: 10.000000 y: 20.000000 z: 30.000000 addmethod() Function We can add a method to the object class using the addmethod() function This method can be used with any object from the same class. Syntax: AddMethod(Object,cNewMethodName,cMethodName|AnonymousFunction) Example: o1 = new point { x=10 y=20 z=30 } addmethod(o1,"print", func { see x + nl + y + nl + z + nl } ) o1.print() Class point x y z Output: 10 20 30 Instead of using anonymous function to add new method to the class, we can use the function name Example: o1 = new point { x=10 y=20 z=30 } myfunc = func { see x + nl + y + nl + z + nl } addmethod(o1,"print", myfunc ) addmethod(o1,"display", myfunc ) addmethod(o1,"show", myfunc ) o1.print() o1.display() o1.show() Class point x y z Output: 10 20 30 10 20 30 10 20 30 Since we add the method to the class, any object from that class can use this method Example: o1 = new point { x=10 y=20 z=30 } o2 = new point { x=100 y=200 z=300 } o3 = new point { x=50 y=150 z=250 } addmethod(o1,"print", func { see x + nl + y + nl + z + nl } ) o1.print() o2.print() o3.print() Class point x y z Output: 10 20 30 100 200 300 50 150 250 getattribute() function We can get the object attribute value using the getattribute() function Syntax: GetAttribute(oObject,cAttributeName) ---> Attribute Value Example: o1 = new point see getattribute(o1,"name") + nl + getattribute(o1,"x") + nl + getattribute(o1,"y") + nl + getattribute(o1,"z") + nl Class Point x=10 y=20 z=30 name = "3D-Point" Output: 3D-Point 10 20 30 setattribute() function We can set the object attribute value using the setattribute() function Syntax: SetAttribute(oObject,cAttributeName,Value) Example: o1 = new person setattribute(o1,"cName","Mahmoud") setattribute(o1,"nSalary",1000000) setattribute(o1,"aColors",["white","blue","yellow"]) see o1 see o1.aColors Class Person cName nSalary aColors Output: cname: Mahmoud nsalary: 1000000.000000 acolors: List... white blue yellow mergemethods() Function We can share methods between classes without inheritance using the MergeMethods() function This function merge class methods to another class. Syntax: MergeMethods(cClassNameDestination,cClassNameSource) Example: mergemethods("count","share") mergemethods("count2","share") o1 = new count { test() } o1 = new count2 { test() } Class Share func one see "one" + nl func two see "two" + nl func three see "three" + nl Class Display Func printline see copy("*",20) + nl Class Count from Display Func test printline() one() two() three() printline() Class Count2 from Display Func test three() two() one() printline() Output: ******************** one two three ******************** three two one ******************** Ring programming language