WEBVTT 00:02.000 --> 00:08.840 Hello again! In this video, we're going to look at string literals. The traditional way to get a string 00:08.840 --> 00:12.920 literal is to take some characters and put them inside a pair of double quotes. 00:13.430 --> 00:16.610 So here we have a string literal, "hello world". 00:17.540 --> 00:19.760 This is a C-style string literal. 00:20.150 --> 00:23.930 It's an array of char which is terminated by a null character. 00:24.920 --> 00:28.050 The problem with this is that you can't really do very much with it. 00:28.340 --> 00:29.810 You can iterate over the characters. 00:30.350 --> 00:33.500 You can print them out and you can access them as a pointer. 00:35.090 --> 00:40.100 One thing that I've often wanted to do with string literals is to take two string literals and add them 00:40.100 --> 00:43.910 together to give a single string literal with all the characters from both strings. 00:43.910 --> 00:47.200 But you can't do that, or at least not directly. 00:48.320 --> 00:53.030 And if you want to do something with it, it's an array, so it's only compatible with things that are 00:53.030 --> 00:54.680 expecting an array of that length. 00:57.300 --> 01:05.070 We mentioned in the last video that you can create your own suffixes for your own objects. In C++ 14, 01:05.340 --> 01:10.440 they actually implemented that for the string type in the library, so you can now have a suffix which 01:10.440 --> 01:12.390 returns a standard string object. 01:13.230 --> 01:18.510 So this hello string here is actually an object of type standard string, and you can do anything 01:18.510 --> 01:20.370 with that, that you can do with a string object. 01:20.910 --> 01:26.070 So you can concatenate them in just a normal string operation and you can pass it to anything which 01:26.070 --> 01:27.450 expects a string object. 01:28.620 --> 01:32.550 This is implemented in its own namespace, so to be able to get this to work, 01:32.550 --> 01:36.510 we need to put using namespace std literals. 01:39.830 --> 01:45.440 So we start off by creating a C-style string literal, then a standard string literal. 01:45.800 --> 01:49.160 We need to include the literals namespace for that to work. 01:50.210 --> 01:53.390 And then finally, we prove that we can do string operations. 01:55.900 --> 01:56.710 So there we are. 01:56.980 --> 02:01.770 And they all display, "hello, world", but in the first case, it's an array and in the other two cases, 02:01.780 --> 02:03.100 it's a string object. 02:04.480 --> 02:08.530 And just to prove that this really is a string and not 02:10.240 --> 02:15.940 something that's a const character, so we've now converted these back to C-style arrays, and you 02:15.940 --> 02:22.110 can't add arrays in C++, so that an error. Cannot add two pointers. 02:23.650 --> 02:24.100 Okay. 02:27.170 --> 02:30.260 In a string literal, some characters have a special meaning. 02:30.500 --> 02:36.650 For example, if we put backslash n, that means it's a new line character, so that's called an escape. 02:37.760 --> 02:42.200 The backslash is called the escape character, so it changes the meaning of the next character. 02:42.500 --> 02:43.650 It means it's not the letter n, 02:44.090 --> 02:45.530 it's a new line character. 02:46.850 --> 02:52.490 Similarly, if we want to put a double quote inside a string literal, we can't just put a double quote on its own 02:52.490 --> 02:54.080 because that would mean the end of the string. 02:54.950 --> 03:00.410 If we put a backslash quote, that means we just want the double quote character to be one of the characters 03:00.410 --> 03:01.580 inside the string literal. 03:03.970 --> 03:08.330 But this can be a bit problematical if you have a string literal with lots of escaped 03:08.440 --> 03:10.540 characters in, or characters that need escaping. 03:10.900 --> 03:16.140 So something like this we have quotation marks, and a backslash, and a backslash. 03:16.360 --> 03:20.890 So we don't want this to be a backslash less than, because there is no such character. 03:21.490 --> 03:23.890 We want this to be a real backslash inside the string. 03:24.610 --> 03:26.530 So to do that, we need a double backslash. 03:29.960 --> 03:35.090 And we also need to put a backslash in front of the quotation marks. Otherwise, the compiler will think 03:35.090 --> 03:36.050 that's the end of the string. 03:36.920 --> 03:40.280 So if you want a string which appears like this, we need to write it as this. 03:40.280 --> 03:48.080 So backslash quote backslash quote, then backslash to the backslash, then backslash quote and then, well, 03:48.170 --> 03:49.370 lots and lots of backslashes. 03:49.700 --> 03:50.540 It's a bit of a mess. 03:51.550 --> 03:54.670 It's not quite clear what this is going to look like. 03:54.680 --> 03:57.260 And also, this is quite right? Three back slashes? 03:58.070 --> 03:59.660 So this is not a great way to do things. 04:04.680 --> 04:10.950 In C++ 11, you can now have a raw string, so you write the string exactly as you want it to appear. 04:11.760 --> 04:19.570 And then you put capital R, double quote, open bracket before the string and then close bracket, 04:19.620 --> 04:21.180 double quote at the end of the string. 04:21.480 --> 04:24.060 So this will turn this into a raw string. 04:28.100 --> 04:33.890 And this means that the double quote and the backslash characters aren't going to be processed 04:33.920 --> 04:36.980 as escaped characters, they'll just be taken literally, if you like :) 04:38.990 --> 04:44.390 So if we run this program and print out this string, then it'll be exactly like that. What happens 04:44.390 --> 04:48.200 if the string contains a bracket, a closing bracket, followed by double quote? 04:48.830 --> 04:50.750 In that case, we add a delimiter. 04:51.380 --> 04:55.850 So we have this which has x86, then closing bracket, then double quote. 04:56.390 --> 04:58.400 So we don't want that to end the raw string. 04:59.240 --> 05:04.730 So what we do is we put this delimiter character x after the double quote, and that means that we need 05:04.820 --> 05:09.380 to have a closing bracket x double quote, before we actually finish off the string. 05:09.590 --> 05:15.590 So this close bracket quote here doesn't end the string. This close bracket x does end the string. 05:16.890 --> 05:17.140 Right. 05:17.910 --> 05:18.510 I hope you got that! 05:21.880 --> 05:27.820 Say here's three different ways of writing the string. So we have the traditional way with lots of back 05:27.820 --> 05:28.360 slashes. 05:30.880 --> 05:37.990 And then we have a raw string, which includes the close bracket, close quote, so we add the delimiter 05:38.000 --> 05:41.560 to make sure that the string doesn't stop there, it goes all the way to the end. 05:42.820 --> 05:44.020 So let's see what we get. 05:46.620 --> 05:47.760 So all of these... 05:50.340 --> 05:54.360 So all of these print out the URL as we want it to appear. 05:54.720 --> 05:59.340 The first one, we had to put all these back slashes in. The second one, we used the raw string. 05:59.850 --> 06:04.230 And then the third one, we had to use the delimiter to make sure we got the entire string and not just 06:04.650 --> 06:05.430 the bit up to there. 06:07.940 --> 06:08.360 Okay. 06:08.930 --> 06:10.610 So that's it for this video. 06:11.210 --> 06:15.200 I'll see you next time, but meanwhile, keep coding!