So we've already talked about strings. Strings are a common construct. You see them in every programming language, and strings are made of unicode Unicode runes. They're straight, basically, a raid of runes. So, there's a package called the Unicode Package which provides a set of functions that actually evaluate the properties of the different runes inside the strings. And it's useful if you've ever done parsing, you know, you want to parse some string out of whatever file. Or out of a- maybe something somebody typed in directly as user input and you want to evaluate that string when you're doing parsing you need functions like these so there a long set of functions that the unicode package provides to evaluate the runes Some of them here, are IsDigit tells you if the rune is a digit, a numerical digit. IsSpace- is it a space character? isLetter is the letter lowercase, IsPunct- is punctuation so these are all binary- boolean right so they return true or false depending on if the rune is what it's saying it to be, if it's a digit or space or so on. There aree also a set of other functions that perform conversions. So some of these conversions ae possible. For isntance ToUpper and ToLower. You can take a lower case (r rune),turn it into an upper case (r rune). And vice versa. So they provide funtions for that. So they take a (r rune), like ToUpper, it takes a (r rune), Which is lowercase and returns a which is uppercase and so on. So a unicode package is useful for that. But there are other packages that are also involved in manipulating strings. There's the strings package. So the strings package. The functions that it provides are things to directly. Not looking at the individual generally, but look at the whole string. So there are a set of search functions it provided. Inside the strings package. These are common functions that you see in lots of different lanugages also. So for instance, the first one would be compare. Compare (a, b), you givev it two strings and it compares to see if they're equal. And actually this compare function, it returns a -1. It returns 0 if they're equal, it returns a -1 if a is less than b, meaning earlier than it, in In alphanumeric order. And A, it returns a positive one, if A is greater than B, so if A is later than B in alphanumeric order. So, to compare, contains, so you give S a string, and then a sub string, if that sub string is contained inside S, it returns true, otherwise false. Have prefix so you give it a string s and a prefix. If that and returns true, if that prefix is the, s starts with a prefix and index s and you go to substring, what that does is a search, it searches for the substring inside s. And it returns you the index of where the first instance, instance of that substring can be found inside a [INAUDIBLE] can be found. So, this is the string's package. Now, the string's package also provides a set of functions that manipulate strings. Now, when I say manipulate, you can say changes string, a string is mutable. But, there are a lot of functions that take an existing string and return a new string. That is some modified and some useful way. So the first one will be replace. With replace you basically take a string and it allows you to replace instances whenever it finds it in a current of old it replaces it with currents of new. So these are all strings. So there's a big string S Is a substring old and another substring new. Replaces instances of old with instances of new. And return to a new string. So s the original string is not actually changed. It returns you to a new string with a replacements for ToLower, ToUpper, so this'll take the whole string and change it to lower case or upper case. I keep saying change. It does not change the string. It returns a new string that is modified. Also, trim space is useful. That gets rid of leading and trailing light space from a string. So you get this a lot when you're reading from a file with, say, and maybe the tokens in the file are seperatedby spaces, so if you just read directly in the file, you'll also read these spaces in, but you don't need the spaces. You just need the token. So you may call TrimSpace to get rid of the spaces. Another package that has a lot of useful functions for strings is the Strconv Package. So generally this provides a set of functions for converting strings from different basic data types, to and from different basic data types. So some of the big ones are Atoi As ascii to integer is what it stands for. And converts a string to an integer if that string represents an integar. Lets say, you are reading a string from a file and the string is a number 123 one hundred and twenty three. Now when you read that, and you read that as a string, You can't do math on a string, right? You can't take that 123 and add 1 to it because it's a string type, it's not an Int type. So you need to read that string in and convert it to an Int. And then you can do math on it. So you'd use Atoi to do a thing like that. And Itoa does the reverse. It converts an Int into a string, an equivalent string. Then FormatFloat basically does a similar thing for float. So it converts a floating point number into a string representation of that floating point number. And then ParseFloat does the opposite, converts a string to a floating point number. So a string, so if you have a string. 123.45, and in a string it can convert it into a floating point the number you can actually do method.
