1 00:00:02,640 --> 00:00:03,330 Hello everyone. 2 00:00:03,360 --> 00:00:06,690 So in this video we will learn about constrained functions. 3 00:00:06,690 --> 00:00:11,880 So before starting question functions let us first to review our code of function class that we did 4 00:00:11,880 --> 00:00:13,380 in the last session. 5 00:00:13,440 --> 00:00:19,710 OK so we have this function class this has two properties numerator and denominator and both the properties 6 00:00:19,710 --> 00:00:20,780 are private. 7 00:00:21,030 --> 00:00:27,210 Then we have a default constructor and then we have a better met base constructor which takes numerator 8 00:00:27,480 --> 00:00:28,930 and denominator as input. 9 00:00:29,390 --> 00:00:30,020 Okay. 10 00:00:30,120 --> 00:00:36,930 So we made these four functions these four functions were not present earlier but now we have made it. 11 00:00:36,960 --> 00:00:37,500 Why. 12 00:00:37,530 --> 00:00:41,950 Because the numerator and denominator property both add private field. 13 00:00:41,970 --> 00:00:46,430 So if we want to exist the numerator and denominator we have to make good friends central functions. 14 00:00:46,890 --> 00:00:50,480 So we have a function get numerator and only then numerator. 15 00:00:50,490 --> 00:00:55,260 Similarly we have a function get denominator so dysfunction returns through the denominator. 16 00:00:55,260 --> 00:00:56,990 Then we have a function set numerator. 17 00:00:57,000 --> 00:01:01,570 It will set the numerator said denominator it will set the denominator. 18 00:01:02,730 --> 00:01:03,280 Okay. 19 00:01:03,330 --> 00:01:10,920 And then we have brain function simplify function add function and multiply function. 20 00:01:10,980 --> 00:01:15,930 So all of these functions were killed in the last class we just created this for new functions. 21 00:01:15,990 --> 00:01:16,580 Okay. 22 00:01:16,680 --> 00:01:20,380 Get any set of functions. 23 00:01:20,460 --> 00:01:24,290 Now we have two objects faction EF 1 and faction EF 2. 24 00:01:24,360 --> 00:01:27,710 Okay so what is this index for creating AI and Deja constant. 25 00:01:27,950 --> 00:01:29,710 So this index is quite familiar. 26 00:01:29,760 --> 00:01:32,040 We are quite familiar with this index. 27 00:01:32,210 --> 00:01:35,190 So in days 5. 28 00:01:35,270 --> 00:01:44,080 Now if I want to create an digit constant and cause to be equal C so this is this index for creating 29 00:01:44,080 --> 00:01:45,230 and data constraint. 30 00:01:45,250 --> 00:01:51,730 Now similarly we can create object constraint we can create constant objects so this indexes fraction 31 00:01:54,320 --> 00:01:58,870 then constant keyword F3. 32 00:01:58,940 --> 00:01:59,290 Okay. 33 00:01:59,300 --> 00:02:02,060 So this is just an index for creating a unconstrained object. 34 00:02:02,060 --> 00:02:07,070 Now if I do B plus plus here this is wrong at everybody. 35 00:02:07,140 --> 00:02:09,660 Because we cannot change its properties. 36 00:02:09,660 --> 00:02:14,740 Similarly we cannot change the properties of f3 because it is a constant friction. 37 00:02:14,760 --> 00:02:17,550 We cannot change the properties of f3. 38 00:02:17,910 --> 00:02:18,540 Okay. 39 00:02:18,750 --> 00:02:19,920 So now let's encode 40 00:02:25,220 --> 00:02:33,140 so let us make a constant object so friction constant keyword F3. 41 00:02:33,210 --> 00:02:35,190 Okay now let us try to print the values. 42 00:02:35,190 --> 00:02:46,790 Let us try to printer's properties numerator and denominator so c out after dot get denominator Saudi 43 00:02:47,000 --> 00:02:50,120 we will first print numerator so numerator 44 00:02:54,420 --> 00:02:57,800 and now let us print denominator. 45 00:02:57,830 --> 00:03:02,020 So I have to don't get a denominator okay. 46 00:03:03,360 --> 00:03:12,850 Now let us try to change the value of numerator also so I have three not set numerator and let us give 47 00:03:12,850 --> 00:03:14,570 the value then. 48 00:03:14,650 --> 00:03:18,100 Okay so let's try to analyze what will be our output 49 00:03:21,010 --> 00:03:25,570 so we are creating a constraint object F3 since it is a constant object. 50 00:03:25,570 --> 00:03:27,620 We cannot change its properties. 51 00:03:27,790 --> 00:03:32,080 Okay but in the get numerator sort of this function is a good numerator. 52 00:03:32,320 --> 00:03:37,060 So in that get the numerator and get the number of function we are not changing the property. 53 00:03:37,060 --> 00:03:39,690 These function are just pretending the properties. 54 00:03:39,790 --> 00:03:40,290 Okay. 55 00:03:40,300 --> 00:03:46,990 So I believe we can call these functions but see this line set numerator so this function will change 56 00:03:46,990 --> 00:03:50,690 the value of numerator since this function change there enough numerator. 57 00:03:50,710 --> 00:03:55,990 We cannot call this function okay we cannot call a function which changes the properties of the object. 58 00:03:56,710 --> 00:04:03,650 So ideally these two will run fine and we will get error at this line we will get that at this thing. 59 00:04:03,650 --> 00:04:03,850 Okay. 60 00:04:03,860 --> 00:04:05,630 So what if I will come the. 61 00:04:05,690 --> 00:04:09,140 Then what will happen at this line. 62 00:04:09,140 --> 00:04:18,480 Default constructor will be called default constructor that we have created so our default constructor 63 00:04:18,480 --> 00:04:23,260 will be called and numerator and denominator property will be said to the god which values. 64 00:04:23,490 --> 00:04:30,630 And when we are printing the numerator the denominator we lose we will get garbage and garbage. 65 00:04:31,050 --> 00:04:31,310 Okay. 66 00:04:31,310 --> 00:04:33,930 Both numerator and denominator will contain language values. 67 00:04:34,500 --> 00:04:36,360 Okay so let us run our file. 68 00:04:36,750 --> 00:04:39,770 I believe we will get at the headline number two. 69 00:04:40,260 --> 00:04:41,460 So now let's see that it 70 00:04:44,590 --> 00:04:53,320 Okay so let's end this file so we are getting at it here because numerator user private property we 71 00:04:53,320 --> 00:04:57,080 have to call function get nominated. 72 00:04:57,130 --> 00:05:02,620 Okay so now let's send this file so I believe what should happen we should get that right line number 73 00:05:02,700 --> 00:05:05,000 one but we are getting an headline number 10. 74 00:05:05,000 --> 00:05:06,860 Now let us see data without that is 75 00:05:10,100 --> 00:05:11,360 so we are getting at it. 76 00:05:12,770 --> 00:05:17,120 Get numerator get dominated and certain numerator. 77 00:05:17,120 --> 00:05:24,150 Basically we are getting error on all the three functions we are getting error for this function get 78 00:05:24,150 --> 00:05:24,990 numerator. 79 00:05:24,990 --> 00:05:30,000 We are getting error for this get denominator and we are getting error for said numerator function. 80 00:05:30,060 --> 00:05:30,530 Okay. 81 00:05:30,630 --> 00:05:33,040 We have discussed we should get better at this line. 82 00:05:33,060 --> 00:05:35,530 But we are getting error at all the two functions. 83 00:05:35,610 --> 00:05:37,860 So that means there is something wrong with our approach. 84 00:05:37,860 --> 00:05:41,320 So our approach is wrong our way of thinking was wrong. 85 00:05:41,370 --> 00:05:42,750 There is something else. 86 00:05:42,780 --> 00:05:48,960 Okay let us try to understand what is wrong with our approach to actually what happens is when you create 87 00:05:49,200 --> 00:05:56,280 a constraint object so friction constant F3. 88 00:05:56,280 --> 00:06:02,430 So whenever you create a constraint object we cannot call any function through F3 we cannot call any 89 00:06:02,430 --> 00:06:08,550 function through F3 because compiler is worried about the function that you have called what is inside 90 00:06:08,550 --> 00:06:12,180 that function we some changes to our properties then it's a problem. 91 00:06:12,180 --> 00:06:12,680 Okay. 92 00:06:12,750 --> 00:06:17,670 So basically the compiler won't allow us to call any normal function through F3. 93 00:06:18,120 --> 00:06:23,460 Okay so compiler will not allow us to call any normal function to a constraint object. 94 00:06:23,460 --> 00:06:28,830 We can only call Constraint Function through constraint objects and not any normal functions. 95 00:06:28,860 --> 00:06:32,070 So now the question came What is a constraint function 96 00:06:37,100 --> 00:06:39,290 so what is the constraint function. 97 00:06:39,290 --> 00:06:43,790 A constraint function that does function that do not change the properties of the object. 98 00:06:43,790 --> 00:06:45,520 Okay so constrain functions 99 00:06:48,490 --> 00:06:50,320 which does not 100 00:06:53,860 --> 00:06:58,360 change which does not change any property 101 00:07:02,700 --> 00:07:03,770 of the current object 102 00:07:09,110 --> 00:07:13,700 Okay so constant functions are those functions which do not change the properties of the object. 103 00:07:14,480 --> 00:07:14,750 Okay. 104 00:07:14,780 --> 00:07:16,550 So I hope you have understood the problems. 105 00:07:16,550 --> 00:07:23,180 The problem is compiler will not allow us to call any normal function because the object is constant. 106 00:07:23,210 --> 00:07:27,200 Similarly we cannot call this function because compiler is worried about us. 107 00:07:27,260 --> 00:07:27,510 Okay. 108 00:07:27,530 --> 00:07:32,340 What if we inside the good denominator function which is the value of the denominator or numerator. 109 00:07:32,470 --> 00:07:36,230 I'll get a compiler won't allow us to call any normal function through a constraint object. 110 00:07:37,040 --> 00:07:39,710 Okay so we have to use constraint functions. 111 00:07:39,710 --> 00:07:42,410 Now let's see how to make a function Constraint Function 112 00:07:45,680 --> 00:07:48,680 so C we have a get numerator function. 113 00:07:48,710 --> 00:07:52,400 So what this get numeral function is doing it is simply returning the numerator. 114 00:07:52,400 --> 00:07:55,830 It is not changing the value of any of the properties of the object. 115 00:07:55,910 --> 00:07:59,120 So I believe we should mark this function as question function. 116 00:07:59,150 --> 00:08:01,740 So how do mark a function of constant function. 117 00:08:01,760 --> 00:08:04,740 We simply have to write a keyword constant. 118 00:08:04,790 --> 00:08:07,320 Now this function is a constraint function. 119 00:08:07,370 --> 00:08:07,870 Okay. 120 00:08:07,940 --> 00:08:10,940 And F3 can call this function similarly. 121 00:08:10,940 --> 00:08:12,400 Get denominator function. 122 00:08:12,440 --> 00:08:19,640 This function is only accessing their denominator property so we can also make this function as constant. 123 00:08:19,640 --> 00:08:24,930 Now the constraint object which is F3 can call this function okay. 124 00:08:25,140 --> 00:08:26,430 Now let's turn this file 125 00:08:31,740 --> 00:08:37,170 and now we will run this file now if we will run this file we will only get it for set numerator function 126 00:08:37,590 --> 00:08:42,030 and not error for getting the denominator end good no matter darn good denominator function. 127 00:08:42,090 --> 00:08:48,870 Okay okay so let's wrap this file so this time we are getting an error at line number 10. 128 00:08:48,910 --> 00:08:54,450 So if you will see that it so here that is only due to set numerator function. 129 00:08:54,600 --> 00:08:55,200 Okay. 130 00:08:55,290 --> 00:09:03,840 That is only due to set numerator function so this time we can call get numerator function and get the 131 00:09:03,840 --> 00:09:07,740 number to function because both the function has been marked as Constraint Function. 132 00:09:07,740 --> 00:09:10,180 So compiler will allow us to call these functions. 133 00:09:10,200 --> 00:09:10,670 Okay. 134 00:09:10,740 --> 00:09:14,630 So what compiler will do when we are calling this function get numerator. 135 00:09:14,670 --> 00:09:17,810 So compiler will go to get numerator function. 136 00:09:18,090 --> 00:09:19,300 So where is good numerator. 137 00:09:19,350 --> 00:09:24,000 So get new compiler will reach here get numerator function and this function is constant. 138 00:09:24,030 --> 00:09:26,380 So compiler will allow us to call this function. 139 00:09:26,460 --> 00:09:32,240 Similarly when you call this function get denominator so compiler will reach get the number to function. 140 00:09:32,340 --> 00:09:38,310 Since this function is a constraint function compiler will allow us to call this function and for set 141 00:09:38,310 --> 00:09:43,400 numerator function compiler will reach said no other function since this function is not constraint. 142 00:09:43,400 --> 00:09:48,230 Compiler won't allow us to call this function okay now. 143 00:09:48,280 --> 00:09:53,740 So tell me whether it said normal the function qualified to a constraint function or not. 144 00:09:53,770 --> 00:09:58,510 So the answer is set no matter the function cannot be a constraint function because it is changing the 145 00:09:58,510 --> 00:09:59,730 property. 146 00:09:59,800 --> 00:10:00,400 Okay. 147 00:10:00,490 --> 00:10:03,830 Now what if I make this function of Constraint Function. 148 00:10:03,880 --> 00:10:04,290 Okay. 149 00:10:04,370 --> 00:10:06,490 Eileen this should not be a constraint function. 150 00:10:06,490 --> 00:10:09,870 Now what if I make this function a constraint function what will happen. 151 00:10:09,880 --> 00:10:17,140 Now let us turn our file C we coordinated why we got an error because here we are trying to change the 152 00:10:17,140 --> 00:10:22,260 value of numerator and since the function is constant we cannot do this. 153 00:10:22,300 --> 00:10:22,780 Okay. 154 00:10:22,960 --> 00:10:24,470 So let's remove constraint here. 155 00:10:25,870 --> 00:10:27,010 Now let's send this file again. 156 00:10:27,940 --> 00:10:29,940 So this time our file is running. 157 00:10:29,950 --> 00:10:37,440 There is no added okay now said delimiter function can be a constant function or not. 158 00:10:37,690 --> 00:10:42,610 So same reason I said numerator side in order function doesn't qualify to be a constraint function because 159 00:10:42,610 --> 00:10:47,980 it is because it will try to change the value of denominator not print function at this dog world brain 160 00:10:47,980 --> 00:10:51,470 function can print function qualify for a question function. 161 00:10:51,490 --> 00:10:54,900 Yes it is because it is only accessing the properties. 162 00:10:54,910 --> 00:10:56,490 It is not changing the property. 163 00:10:56,560 --> 00:10:58,220 It is not trying to change that property. 164 00:10:58,240 --> 00:11:01,530 So brain function is a constraint function. 165 00:11:01,530 --> 00:11:05,100 Now let us talk about simplifying can it be a constraint function. 166 00:11:05,110 --> 00:11:06,150 The answer is No. 167 00:11:06,180 --> 00:11:06,430 Why. 168 00:11:06,430 --> 00:11:12,370 Because it is changing the value of because it is changing the properties so it cannot be a constraint 169 00:11:12,370 --> 00:11:14,380 function and function. 170 00:11:14,380 --> 00:11:20,230 It is also changing the properties numerator and denominator so it cannot qualify for a Constraint Function. 171 00:11:20,230 --> 00:11:21,290 Multiply function. 172 00:11:21,290 --> 00:11:26,090 It is also changing the numerator and denominator so it cannot be a constraint function. 173 00:11:26,140 --> 00:11:34,150 Okay so only brain function so only brain function and these two functions are qualifying for the constraint 174 00:11:34,150 --> 00:11:35,470 functions. 175 00:11:35,470 --> 00:11:36,210 Okay. 176 00:11:36,640 --> 00:11:41,200 So whenever we are working with the classes and objects whenever we are working with the functions we 177 00:11:41,200 --> 00:11:46,000 should look carefully it'll function can qualify for a constraint function then I believe we should 178 00:11:46,000 --> 00:11:51,610 make them a constraint function so that constraint object can call these functions. 179 00:11:51,610 --> 00:11:53,080 Okay thank you.