WEBVTT 00:00.150 --> 00:07.050 In a previous lecture we learned about argument passing and now I want to talk about having default 00:07.080 --> 00:08.080 arguments. 00:08.340 --> 00:16.590 So let's say we had this example where AB function returns an integer and it calculates the volume of 00:16.620 --> 00:25.620 a rectangular prison given the width length and height and all the function does is multiply the width 00:26.010 --> 00:28.230 and height and returns it. 00:28.230 --> 00:36.150 So in the main we have just three variables and we just set them all to five here and then we just pass 00:36.150 --> 00:38.940 them into the function call. 00:39.180 --> 00:47.110 And if it were an inch see the outputs volume is 125 K.. 00:47.180 --> 00:52.770 So if you wanted to you have a default parameter here. 00:52.960 --> 01:00.210 Let's say we want to have the default of height to be 5 k. 01:00.420 --> 01:13.620 So all we do is in the declaration of the function we set this right most parameter and it has to be 01:13.620 --> 01:18.040 the rate most parameter for a reason not get into that later. 01:18.390 --> 01:20.910 And we just said it to be equal to 5. 01:20.910 --> 01:27.430 Notice that I'm not going to set the definition to be five here. 01:28.460 --> 01:28.880 OK. 01:28.900 --> 01:32.900 This is not needed at all. 01:32.930 --> 01:35.570 In fact it's an error if you do it. 01:36.040 --> 01:41.010 OK so it only happens in the declaration. 01:41.060 --> 01:47.730 Now we don't actually need to send the height to the function call anymore. 01:48.900 --> 01:51.030 OK because we already have it defaulted. 01:51.070 --> 02:02.060 So if you run this again see it's still 125 even though we didn't set the height variable in the call 02:02.690 --> 02:04.100 to the function. 02:04.120 --> 02:05.780 In fact it could change the 02:08.590 --> 02:18.190 default to be 10 and can rerun this and it's 250 Rantz five times five is twenty five times ten is 250 02:18.810 --> 02:19.230 K. 02:19.390 --> 02:29.440 So it's actually using the default here and even do you even have length beautyful so say length is 02:29.440 --> 02:38.910 the default of two k and then we don't actually have to have length here. 02:39.030 --> 02:45.180 And if you run this it's a it's five times two right. 02:45.220 --> 02:46.580 It's ten times ten. 02:46.580 --> 02:48.250 It's 100 days. 02:48.250 --> 02:51.530 It's using the default length. 02:51.810 --> 03:01.690 We could in fact have link here and right here it should be under-25 like it was before. 03:02.020 --> 03:12.040 So you don't need to have or you don't have to have the length in height here but if you don't it'll 03:12.070 --> 03:17.170 just default to do whatever you had here. 03:19.610 --> 03:26.480 So but you can still call it just like normal if you want. 03:26.980 --> 03:35.860 So knows here that we have the height redefault in order to have the length of the fault. 03:36.180 --> 03:43.440 So otherwise the call to this function would be ambiguous it wouldn't understand what parameter you're 03:43.440 --> 03:44.100 talking about. 03:44.100 --> 03:53.040 You couldn't have something like this where length is not default which is OK. 03:53.130 --> 03:59.890 You tried to run this it'll give you an error says error missing default argument on parameter length 04:00.630 --> 04:09.480 and so saying so we're really saying the order in which you have defaults really matters and the way 04:09.480 --> 04:18.480 I think of it is you always want to start from the rightmost parameter and work your way inwards. 04:18.540 --> 04:20.790 Otherwise it's not going to work properly. 04:21.690 --> 04:26.480 So this way. 04:26.840 --> 04:37.040 So in the next section or in next lecture I'm going to talk about some looping with functions themselves.