1 00:00:01,630 --> 00:00:02,440 Hello everyone. 2 00:00:02,440 --> 00:00:07,810 So in the last session we created a friction class and now we will discuss some important concepts that 3 00:00:07,810 --> 00:00:09,790 were not covered in the last session. 4 00:00:09,790 --> 00:00:13,090 Okay so first let us analyze this friction class. 5 00:00:13,210 --> 00:00:17,790 So in this friction glass we have two private properties numerator and denominator. 6 00:00:17,830 --> 00:00:18,970 Then we have a better match. 7 00:00:19,030 --> 00:00:22,930 I used constructor a brain function and I'll add a function. 8 00:00:22,930 --> 00:00:23,480 Okay. 9 00:00:23,500 --> 00:00:26,320 And then we created simplify a function at the last. 10 00:00:27,150 --> 00:00:27,370 Okay. 11 00:00:27,370 --> 00:00:30,700 So this is all about the function glass okay. 12 00:00:30,700 --> 00:00:31,930 Now let's see. 13 00:00:31,930 --> 00:00:35,950 Now let's analyze the function and what is happening in that function 14 00:00:40,610 --> 00:00:47,700 so we have two fractions so the numerator and denominator for first reaction was tending to this is 15 00:00:47,700 --> 00:00:55,700 faction f 1 and numerator ended on the default affection 2 was 15 food and this was our affection to. 16 00:00:55,920 --> 00:01:03,450 So how we are calling this added function f one dot at and b bus F2 US barometer. 17 00:01:04,070 --> 00:01:04,550 Okay. 18 00:01:04,650 --> 00:01:09,670 So what is happening here is we are making a copy of F2 head. 19 00:01:09,780 --> 00:01:10,070 Okay. 20 00:01:10,080 --> 00:01:12,810 So a copy is being generated. 21 00:01:12,810 --> 00:01:24,580 So what is happening here is we can we can write this line is fraction F2 is it to fraction F2 from 22 00:01:24,580 --> 00:01:25,630 the mean. 23 00:01:25,630 --> 00:01:26,200 Okay. 24 00:01:26,350 --> 00:01:32,790 So this barometer reflection F2 disparagement affection F2 is equals to the fraction from the mean. 25 00:01:32,800 --> 00:01:39,570 So what is happening here is we are creating we are creating a new object and all the values are being 26 00:01:39,570 --> 00:01:40,330 getting copied. 27 00:01:40,750 --> 00:01:41,020 Okay. 28 00:01:41,050 --> 00:01:47,420 So what is happening here is copy construct Baz being getting called copy construct that is correlated. 29 00:01:48,540 --> 00:01:49,030 Okay. 30 00:01:49,150 --> 00:01:56,320 So at Line number 17 at line number 17 copy constructor is being getting called a copy constructor is 31 00:01:56,320 --> 00:02:03,360 creating an object and then it copies the value from the fraction which is present in mean okay. 32 00:02:03,420 --> 00:02:04,650 So what our aim is. 33 00:02:04,650 --> 00:02:12,640 So our aim is our aim is very simple we want to avoid the copy we don't want to copy okay. 34 00:02:12,770 --> 00:02:14,670 We want to avoid this copy. 35 00:02:14,900 --> 00:02:17,220 So why do we want to avoid this copy. 36 00:02:17,330 --> 00:02:23,060 Because if you look in the if you look inside the added function we are only accessing the properties 37 00:02:23,060 --> 00:02:24,290 of fraction F2. 38 00:02:24,560 --> 00:02:27,680 We are only using the properties of friction F2. 39 00:02:28,490 --> 00:02:34,610 So why do copy if we will copy then there is time in memory waste because first and object will be created 40 00:02:34,820 --> 00:02:36,830 then all the values will be copied. 41 00:02:36,830 --> 00:02:39,830 Okay but we only need to access its properties. 42 00:02:40,010 --> 00:02:41,360 So there is no need to copy. 43 00:02:41,360 --> 00:02:44,830 So ultimately our aim is we have to avoid this copy. 44 00:02:44,840 --> 00:02:47,840 Now how can we avoid this copy is the question. 45 00:02:48,110 --> 00:02:49,910 So how can we avoid this copy. 46 00:02:49,910 --> 00:02:56,230 So we all know we have started about our offense is variable and passed by it offense in function. 47 00:02:56,360 --> 00:03:00,500 Okay so what we will do we will pass by reference to avoid copy. 48 00:03:00,500 --> 00:03:01,790 So let us take an example. 49 00:03:02,600 --> 00:03:09,760 So when we write in days 5 and into G is I. 50 00:03:09,790 --> 00:03:11,730 What happened at this line. 51 00:03:13,200 --> 00:03:16,850 This is the scenario and at this line a memory block will be created G. 52 00:03:16,880 --> 00:03:24,400 And the value will be copied but we want new blocks should not be there so we will use a reference variable. 53 00:03:24,440 --> 00:03:31,290 So what will the effect of this line the effect of this line is is very simple K okay. 54 00:03:31,310 --> 00:03:37,060 The boat points to the same memory block I n Cape belongs to the same memory block. 55 00:03:37,070 --> 00:03:41,000 So if I were Lou Gabler surplus then this value will become 6. 56 00:03:41,370 --> 00:03:47,410 Okay so if you do see out okay or if you see out I output will be 6. 57 00:03:47,750 --> 00:03:49,130 Order will be 6. 58 00:03:49,130 --> 00:03:53,280 Both AI and key points to this memory block. 59 00:03:53,330 --> 00:03:54,920 Okay I can change. 60 00:03:54,980 --> 00:03:56,090 I can read and write. 61 00:03:56,110 --> 00:04:00,680 Data can also read and write data so we will use a reference variable. 62 00:04:00,680 --> 00:04:10,160 So this scenario will look something like this faction reference variable is main guard F to okay. 63 00:04:10,230 --> 00:04:13,690 So in this way we will be able to avoid copy. 64 00:04:13,740 --> 00:04:15,970 Okay so let's see. 65 00:04:16,090 --> 00:04:21,260 So what we have to do we will avoid copy using the reference variable. 66 00:04:21,320 --> 00:04:23,310 Now there is still a problem. 67 00:04:23,450 --> 00:04:24,820 What is the problem. 68 00:04:24,860 --> 00:04:34,750 So suppose if I do something like this after dot numerator is minus 1 I am changing the values of F2 69 00:04:34,810 --> 00:04:38,400 I'm changing the numerator property of F2. 70 00:04:38,540 --> 00:04:48,510 So my aim is my aim is to avoid this to avoid this. 71 00:04:48,540 --> 00:04:50,840 No one can change the values of numerator. 72 00:04:50,850 --> 00:04:53,640 No one can change the values of F2. 73 00:04:53,640 --> 00:04:56,740 So how can we do this. 74 00:04:56,830 --> 00:04:58,260 So how can we achieve our goal. 75 00:04:59,430 --> 00:05:00,450 So it's very simple. 76 00:05:00,480 --> 00:05:01,110 What do we do 77 00:05:04,610 --> 00:05:13,240 so when we write in day is five and end at events where DeBakey is I. 78 00:05:13,290 --> 00:05:16,120 What happened is this is I. 79 00:05:16,130 --> 00:05:17,300 And this is key. 80 00:05:17,450 --> 00:05:20,130 I can I can read and write data. 81 00:05:20,250 --> 00:05:22,250 Key can also read and write data. 82 00:05:22,550 --> 00:05:31,670 But there should be a V if I do get plus plus then add I should be dead I want cake and only read data. 83 00:05:31,760 --> 00:05:35,020 Gays should not be able to write data gay can only read data. 84 00:05:35,500 --> 00:05:36,210 So what to do. 85 00:05:36,580 --> 00:05:39,680 So we have a constant reference variable. 86 00:05:39,790 --> 00:05:40,460 Where do we. 87 00:05:40,480 --> 00:05:46,450 This index will look something like this and constant reference variable key is I. 88 00:05:47,770 --> 00:05:54,310 So gays a reference variable to won't be the constant gays at offensive Eddie Baldwin Deja constant 89 00:05:54,490 --> 00:05:56,240 so gay is a constant preference. 90 00:05:56,260 --> 00:05:58,490 So if we will use this then what will happen. 91 00:05:58,510 --> 00:06:01,500 So this is five I am gay. 92 00:06:01,580 --> 00:06:02,690 Both points here. 93 00:06:02,840 --> 00:06:08,620 I can read and write data but gay can only lead you down gay cannot write data. 94 00:06:08,900 --> 00:06:09,440 Okay. 95 00:06:09,440 --> 00:06:11,680 Gay Gay cannot write data. 96 00:06:11,960 --> 00:06:16,990 So we need something like this in our program. 97 00:06:17,010 --> 00:06:18,260 So what do we do. 98 00:06:18,300 --> 00:06:24,960 We will create a constant defense so constant reference Okay so whenever we are working on a project 99 00:06:25,200 --> 00:06:27,860 we should keep all these things in our mind. 100 00:06:27,910 --> 00:06:30,340 Now get these small small things matters. 101 00:06:30,550 --> 00:06:36,120 Okay so you should always think that by that I should pass up constraint or offense or simply pass by 102 00:06:36,120 --> 00:06:36,660 value. 103 00:06:36,960 --> 00:06:38,710 Okay so these things matters. 104 00:06:38,790 --> 00:06:40,200 These things really matters a lot. 105 00:06:41,190 --> 00:06:45,440 Okay now let us create one more function a function called Multiply. 106 00:06:45,720 --> 00:06:50,100 Just like that function we are creating one more function which is called multiply so multiply. 107 00:06:50,100 --> 00:06:50,780 We do. 108 00:06:50,970 --> 00:06:59,360 So multiply function will multiply two fractions and how we will call if one dart multiply F2. 109 00:06:59,460 --> 00:06:59,710 Okay. 110 00:06:59,750 --> 00:07:02,130 We will pass one argument. 111 00:07:02,130 --> 00:07:06,520 So our aim is same as the aim which was for our function. 112 00:07:06,900 --> 00:07:13,410 We will multiply F1 and F2 we will multiply if an F2 end store that is right in F1 okay. 113 00:07:13,410 --> 00:07:15,030 F2 will remain unchanged. 114 00:07:15,030 --> 00:07:16,860 It is true that is worked in F1. 115 00:07:16,950 --> 00:07:19,270 So how to multiply two factions. 116 00:07:19,350 --> 00:07:24,630 Suppose F1 is ten by two and we have another function f 2 which is 15 by 4. 117 00:07:25,590 --> 00:07:32,470 So multiplying numerator with the numerator and multiplying denominator with denominator so 150 by 8. 118 00:07:32,670 --> 00:07:38,090 And then we will call simplify function then we will call simplify function. 119 00:07:38,130 --> 00:07:40,680 Okay simple easy. 120 00:07:40,680 --> 00:07:41,610 Now let's write the code 121 00:07:51,060 --> 00:07:53,560 so the return type will be void. 122 00:07:53,610 --> 00:08:00,300 Let's say the name of the function is multiply it will take a function as input. 123 00:08:00,430 --> 00:08:05,560 We will take a constant reference because we do not want our copy construct to be called here because 124 00:08:05,560 --> 00:08:07,750 there is no need to copy okay. 125 00:08:07,840 --> 00:08:13,960 There is no need to copy is a way to call copy constructor and waste our time in memory so we have to 126 00:08:13,960 --> 00:08:15,450 multiply the numerator with the numerator. 127 00:08:15,640 --> 00:08:24,050 So numerator of F1 is numerator of F1 multiply numerator of F2. 128 00:08:24,100 --> 00:08:28,280 So we have to not numerator. 129 00:08:28,300 --> 00:08:31,320 Okay so using this is optional here. 130 00:08:31,500 --> 00:08:32,520 This is optional 131 00:08:35,750 --> 00:08:41,060 so we have to make the better denominator with debt limit as our denominator of F1 is the number of 132 00:08:41,060 --> 00:08:42,070 F1. 133 00:08:42,510 --> 00:08:51,760 Multiply denominator of F2 and then after multiplication is done we have to call simplify function. 134 00:08:52,090 --> 00:08:52,740 Okay. 135 00:08:52,750 --> 00:09:00,550 After multiplication we have to do we have to call simplify function now after degradation let's multiply 136 00:09:00,550 --> 00:09:04,230 a finite F2 so F1 God multiply. 137 00:09:04,690 --> 00:09:13,430 We have to pass off to his argument and now let us spend the value of f1 enough to so F1 not print F1 138 00:09:13,430 --> 00:09:18,310 dart print and similarly large print F2. 139 00:09:18,310 --> 00:09:22,950 So after dot print OK so that's all 140 00:09:30,280 --> 00:09:35,800 so these are the values of our finite F2 after the reason and these are the values of F1 I have two 141 00:09:35,800 --> 00:09:40,420 of them multiplication so we can see here the value of F2 remains unchanged. 142 00:09:40,630 --> 00:09:46,620 And when these two are multiplied we will get this result five twenty five by sixteen. 143 00:09:46,660 --> 00:09:54,640 Okay so go to this code and try to understand each and every line of the code so that's all from my 144 00:09:54,640 --> 00:09:55,470 side. 145 00:09:55,480 --> 00:09:55,900 Thank you.