Lecture 9- Constructors in C++ (Part 2)

[Music] [Music] so welcome to lecture number nine classes and objects so in the last lecture we had seen default Constructor and parameterized Constructor all right so with the help of parameters Constructor so can we solve this particular problem all right so the problem is create a complex number class right the name of the class is complex numbers and add two complex numbers right it is nothing so C1 is A1 + ib1 C2 is equal to A2 + ib2 in fact we had seen the multiplication so C1 + C2 so let us say C3 is C1 + C2 so which will be A1 + A2 + I into B1 + B2 right so this we know so let us solve this using the parameter Constructor all right so the main idea is so when you are adding two complex numbers you take one number from user so let us say C1 I'm taking from the user and C2 should be pass using the Constructor so you're passing so when I am passing means I have to use as argument right so that means it is having the parameter so that means it is a parameterized Constructor so another input should be using the Constructor so let us see how we are going to write this in C++ so let us have the class complex so the class complex has two member data real and imaginary almost similar thing we had seen the multiplication of two complex numbers and here you have the parameterized Constructor so we had seen the name of the class is complex and the name of the special member function is also complex so obviously this is a Constructor and we are using two parameters r and i the real imaginary so therefore you call this as a parameterized Constructor so you have used the parameterized Constructor so R will be initialized right whatever you're passing that will be initialized to real and whatever you are passing for I that will be initialized to imaginary all right so this is a special member function a Constructor line number 11 to 14 now here you go you have line number 17 correct so line number 17 you have a member function called add all right you have a member function called add so we have two arguments so one is C1 and another one is C2 so two complex numbers we have already calculated how to add that means C1 do real plus C2 real A1 + A2 right so this is what we worked out A1 + A2 that means that real numbers the real part will be added and then imaginary part should be added so the real part will be added put some real and another variable sum imaginary so C1 do imaginary plus C2 do imaginary put it in Su imaginary and you are returning complex Su real and Su imaginary all right return the object all right the name of the object is right the complex with some real and some imaginary correct so we will see how this is working when we are going to talk about the main so now line number 24 you have wide display one of the member functions all right so it is printing real plus I into imaginary or imaginary I okay so 2 + 3 I that's a usual way all right so that will be displayed over here so now what was the problem one input you have to take from the user all right so it is asking user real and user imaginary all right so we have a double the main program is starting here user real and user imaginary so we take the input from the user for example assume that so 2 + 3 I is my input user input all right so now here you go I have user complex object right user complex object object I am pausing user real and user imaginary right so whatever I have taken the input from the user I passing this so this is object user complex so that means this will invoke all right whenever you are creating an object this will invoke The Constructor all right so the Constructor will be invoked suppose I'm passing two 2 + 3 I right yes so real will be two and imaginary will be three all right in the first case so that means under user complex object my real will be two and imaginary part will be three all right and you have another object called Constructor complex so the Constructor complex you have you are passing 3.5 and 2.0 so one we set user has to give us a input another one you are pausing so this is an example all right so 3.5 and 2.0 assume that 3.5 + 2.0 I right so when this object is being created again the Constructor will be called so under this object name what is the object name Constructor complex so your real will be whatever number you have passed and imaginary will be whatever number you have passed so I pass 3.5 and 2.0 all right so this is by user and this is by Constructor right I hope you understood so now we will see further all right so now we are calling all right so let us say complex result result is an object all right so complex result result is an object so that object is invoking AD right so that object is invoking ad so you are pausing user complex and Constructor complex all right so this is what exactly we are doing in the case of add complex C1 so now C1 is user right user complex C1 is nothing but user complex and C2 is nothing but Constructor complex so now here C1 and C2 so the corresponding C1 real and C2 real will be added right user complex real part and user complex right Constructor complex real part will be added similarly the respective imaginary part will be added now it is some real and some imaginary all right so now it is returning complex all right so which is carrying some real and some imaginary all right for example if I'm adding 2 + 3 a and 3 + 5 3.5 + 2.0 I all right what I will get 5 .5 + 5.0 I all right so this will be returned in line number 20 all right so when it is return if you look at the main program that will be stored in result all right so that means result do real will be 5.5 and result do imaginary will be 5.0 right so you can see over here right so that will be returned to result so result that carry real part and imaginary part so whenever I have a complex right the object so here the object is result so the result that has real and imaginary look at line number six and seven all right so that will be returned and uh right this uh result. add when it is invoked the addition will be returned to result so the result as real part and imaginary part so so now see how user complex number you are displaying what is user complex number so let us say 2 + 3 I right suppose 2 and three are the input 2 + 3 I this will be displayed and Constructor complex will be displayed now sum of these two complex numbers so that is why the objectoriented program will be elegant all right so you have done everything in the class all right and then when the member function is doing all the addition the Constructor is doing all the addition right Constructor initially saving initializing and then you have a member function that will be doing the addition all right so now here you have result do display some of the complex numbers result. display so that means the result as real number real part and result as the imaginary part so that will be display all right suppose let us assume my input is I am giving 5.0 and 2.0 as a input user input right so we have already passed 3.5 and 2.5 that is a Constructor if you look at the program we have passed this 3.5 and 2.0 right 3.5 and 2.0 5 comma 2 is my input user input user complex all right so when I add this 5 + 3.5 is 8.5 2 + 2 is 4 so I will get the output 8.5 + 4 I so the addition of two complex numbers right so the crucial part here is so when you are declaring the object instanciate an object result right in the right hand side this object result is invoking ADD at member function so you pausing user complex so this will be considered as C1 inside the function and this will be considered as C2 inside the function right copying the usual one all right call by value call by reference all right so here it is C1 you're pausing all right user complex and you're pausing Constructor complex all right so when you are passing this this will be assigned to C1 and C2 it's exactly happening over here and then the corresponding reals will be added corresponding imaginary will be added and line number 20 it is returning the complex object all right which is carrying some real and some imaginary all right so it is nothing but you look it is a special member function kind of right complex some real some imaginary right so here you have when you look at the Constructor complex r i r will be assigned to real and I will be assigned to IM imaginary this is what exactly happening all right and then where it is returning you can see that it will be returned to the result so that means the result as real part result as imaginary part so that is what exactly we are displaying in line number 52 and 53 okay so this is how this particular program is working using parameterized Constructor so you can do the same problem in one more way right so how to do that the same all right so we have imaginary we have this Constructor it's it is nothing but a parameter Constructor up to line number 15 it is same and here you go so here we have complex add all right I have complex reference variable other all right is exactly like few classes back we have done all right addition of two distances if you remember all right feet and inches so here you have real with the other real right imaginary with the other imaginary so we'll see how this will be working and rest of them are same we are going to return the some real and some imaginary whatever we had seen in the previous program and the display function right so only this part is crucial we are going to see how this is working so now the user real and user imaginary all right so when you are creating this particular object the Constructor parameterized Constructor will be invoked with the user real and user imaginary and then another one is Constructor complex you are pausing the value 3.5 and 2.0 exactly the same value we are passing only the line number 16 to 21 all right so it is a different way in fact we had seen this I'll explain one more time for the other example so now you you can see this right right you have declared complex result now the user complex the user complex is invoking at member function and you're pausing Constructor complex right user complex is invoking ADD member function and then you're pausing Constructor complex all right so if you look at the syntax it goes like this complex and others complex reference other which will be equal to right so complex and other correct which will be equal to Constructor complex all right so the meaning is other and Constructor complex is pointing out the same location all right you're copying the reference right pass by reference all right so user complex is invoking ADD function you're passing Constructor complex so complex reference operator other so both are pointing to other which is available in your ad function right that is also a complex object right complex class other object is a complex class and Constructor complex which is also a complex class so they are going to point out the same location right so content will be same so suppose I have what is that Constructor complex you 3.5 comma 2.0 means other will also have now 3.5 comma 2.0 okay that is a meaning so since here your user complex is invoking the function right since a user complex is invoking the function you are real user complex real whatever you are right writing as a input giving as a input user complex all right so that will be your actual real and the imaginary the user complex since it is invoking so the user complex real will be real here and user complex imaginary will be imaginary here and then rest is same you are adding the corresponding real part and you are adding the corresponding imaginary part so then you are returning now rest of the things are same whatever we had seen in the previous program all right when you run the code right so now it is everything is same so only here it is crucial line number 44 is crucial user complex is invoking so that means user complex. real will be the real that you are using in the function and user complex complex right imaginary user complex imaginary will be imaginary right so now you display the user complex numbers Constructor complex numbers and the sum of these two so when I run the code assume that 5 comma 2 is my input all right assume that 5 comma 2 is my input and 3.5 comma 2.0 we are pausing all right so we will get the output 8.5 + 4 I all right so 5 + 3.5 8.5 2 + 2 is 4 all right so this is how we can have the usage of parameterized Constructor right so in one case we have done the result is invoking the add function all right you are pausing two two arguments C1 and C2 user complex and the Constructor complex correct and then it will be copied to C1 and C2 and then rest is same the corresponding the real numbers the real part will be added real parts will be added and the corresponding imaginary part will be added so the complex addition have been done all right so this is the case when the object result itself is invoking add all right so in another case here you have the user complex object is invoking the add member function and then you are passing Constructor complex so when you're are passing the Constructor complex the user complex do real will be the usual real in the function right that is line number 18 and user complex imaginary will be the imaginary in the function right so other anyway the other will be copied all right so that means this Constructor complex will be copied into other so other do real and other do imaginary so the corresponding real part and the corresponding imaginary parts will be added and then that is returning some real and some imaginary so when we are running the code all right so we are getting the same output so this is how we can use the applications of the parameter Constructor so we had seen several applications on the default Constructors and the parameters Constructor so in the parameters Constructor this particular problem it is slightly interesting because the two input that means the real and imaginary you are taking from the user another one you are pausing as a Constructor so slowly you are getting familiar with these object classes the constructors concept right apart from that we had also seen is it possible to define the member function outside the class so in a similar way so the special member function Constructor you can think of whatever program that we have written done so far so is it possible that can we write this Constructor outside the class with the syntax that we have used so the next concept we are going to see copy Constructor right so what do you mean by copy Constructor so here let us assume we have the class example all right so let us assume we have class example I have one member data in a right so I have one member data int a right so here I have one parameterized Constructor the usual one parameterized Constructor now you know example all right so which is same as the name of the class which is same as the name of the class and you are pausing one parameter Index right so you are pausing one parameter which is index so here you have it's a special member function so I'm copying X into a that means a equal to X I'm copying X into a so AAL to X and now here I have another Constructor so this is the copy Constructor all right so here you can see the name of the class example and I am using object reference all right so example is a class and here the object reference address OB all right and ob. a the object. a is equal to a right so in fact a equal to ob. a right ob. a is assigned to a I mean to say right so a is equal to ob. a so this we call it as copy Constructor so we will see in the main program how we can use this all right so here you go your class is over here line number 15 your class is getting over so now this is the usual one when you are calling when you are creating the object E1 all right so you're creating an object E1 by passing the value 36 all right so what is exactly happening in line number 19 all right so that means you are calling the parameters Constructor right you're creating an object E1 passing the value 36 all right so the meaning is you are invoking all right in fact this will be the E1 right when you're creating E1 so it is automatically invoking Constructor so here in this case parameters Constructor because you are passing the value 36 all right so that means a is taking the value 36 so here you are pausing so inex so X is 36 so 36 will be copied into a all right so a equal to 36 for the object E1 for object E1 right so it is nothing but e1. a which is equal to suppose I'm accessing this from outside right in fact it is outside e1. a is 36 all right so the next line so slightly different first time we are seeing you have the class example and then you have object E2 so object E2 you are pausing another object E1 right what is the meaning of this E2 you're pausing another object all right so that means your example is the class name of the class address OB which is equal to what you are passing E1 all right so when you're creating this object E1 will have some memory all right so let us say this will be the location 4 all right when I display E1 see out E1 so it will give 4 location 42 so now when I have this right example reference operator OB whereas if you look in the main I'm passing e 1 all right I passing E1 so when I'm passing E1 right so here you go OB and E1 which is pointing to the same location right OB and E1 which is pointing to the same location all right so we know e1. a is what 36 e1. a is 36 so OB is pointing to 40 02 E1 is also pointing to 42 assume that this is some exad decimal numbers correct so e1. a is 36 that we know already right so now if e1. a is 36 what is ob. a that is also 36 because both are pointing to the same location correct ob. a is 36 so that you are assigning to a that is a meaning OB a is a all right so now when I want to print e2. a all right so that means when I'm creating an object ob. a you are passing right assigning to a meaning is you are e2. a which is also 36 that is the meaning all right ob. a you are assigning to a ob. a is what 36 so here when it is equal to right a equal to ob. a so a equal to 36 for object E2 otherwise you call it as e2. a is 36 all right e2. a is 36 so when I want to display this line number 21 C out is e2. a so you know the output so what will be the output we'll get we will get the output 36 all right I hope it is clear for everyone and line number 20 20 if you look so this is called the copy Constructor right first time we are seeing we have seen default Constructor we had seen parameters Constructor and this is a Syntax for the copy Constructor so object E2 is an object and you're pausing object that object is E1 you're pausing the object E1 so and then once you are pausing this so this is the syntax so example address OB which is equal to E1 right example address OB which is equal to E1 and then if you look over here both OB and E1 is pointing to the same address so that means e1. a is 36 ob. a is also 36 all right so when ob. a is 36 when you are assigning to a so this will be nothing but e2. a all right the meaning is this is nothing but e2. a what is the value of e2. a 36 so when you are trying to display this in the main e2. a you are getting 36 all right I hope it is clear for everyone and the last concept that we are going to see in C++ is the distractors right in today's last class so let us consider the class employee all right so here you have the default Constructor all right so default Constructor you are displaying Constructor inv and then first time we are seeing this is distractor all right so this is distructor so distructor symbol is Tilda and then you have employee same almost like a Constructor but only difference is you put the Tilda symbol so that is nothing but distractors right when you're creating a memory all right when you're are creating an object you require the Constructor all right for the memory and then you have to destroy the memory so for that you require distractors so you might have used the new operator and delete operator right in the case of aray right so new operator is for allocating a memory and and delete operator is for destroying the memory all right deallocating the memory so for the deallocation we have the distractors right assume that you have an object E1 whose class is employee right so you are just printing see out address E1 I'm printing address of E1 right I'm printing the address of E1 and another object E2 I'm printing address of E2 so when you are creating an object Constructor will be called right when you're creating the object Constructor invoke will be displayed right so Constructor invoked I'll just simply write CI stands for Constructor invoked and address of E1 it will print some number right exad decimal number address of E1 and employee E2 Constructor will be invoked and address Z2 some other address 0x 2 3 E7 something like that I'm writing some other address and then return zero so before that you will have the distractor that means you are deallocating the memory for E1 and E2 all right so two more output you will get because of two objects so you will get distractor invoked right so I'll write da two times continuation da da stands for distructor invoked CA stands for Constructor invoked so this you have to get these four as output right so you can see here right Constructor invoked whenever you have employee E1 then you have address E1 employee E2 Constructor invoked and then you have address and finally before going to the return zero both E1 and E2 because of this till the employee the distructor so what you can do you can try without line number 10 and 13 right without line number 10 and 13 you try the same program the last two output will not be displayed right so this is the usage of the distor that means now this memory space right so these two will be D ocated that mean the object E1 and E2 are deallocated from this memory space so that is the meaning right that is what you are getting as a output so in today's class so we talked about the parameterized Constructor and then the applications that we had seen in terms of addition of two complex numbers we had also seen one more Constructor called copy Constructor and now you know the meaning of distructor as well thank you [Music]