--- title: Intro to values and types in go slug: intro-to-values-and-types-in-go published_at: 2020-09-09 17:15:02 +0000 updated_at: 2026-03-04 20:14:47 +0000 summary: description: tags: [values, golang, go, learn to code, computer science] views: 86 author: CJ Avilla url: https://www.cjav.dev/videos/intro-to-values-and-types-in-go youtube_url: https://www.youtube.com/watch?v=b7c8K8HFpOo youtube_id: b7c8K8HFpOo embed_url: https://www.youtube.com/embed/b7c8K8HFpOo thumbnail_url: https://i.ytimg.com/vi/b7c8K8HFpOo/hqdefault.jpg type: video --- # Intro to values and types in go *Published: September 09, 2020* *Views: 86* ## Watch [Watch on YouTube](https://www.youtube.com/watch?v=b7c8K8HFpOo) [![Intro to values and types in go](https://i.ytimg.com/vi/b7c8K8HFpOo/hqdefault.jpg)](https://www.youtube.com/watch?v=b7c8K8HFpOo) ## Description ## Transcript a computer program is a list of instructions that can be followed by a computer to perform a specific task most programs work by taking some input data processing that and creating some output data understanding the values and types will form a foundation on top of which we can build up concepts that will allow us to write our own programs so values are the actual underlying raw numbers and text our program manipulates tony stark the number 43 and false are all examples of values sometimes we'll say that when we literally write the number four and then the number three next to each other to form the number 43 that we're writing the literal 43 same with tony stark if we write the quotes then the letters t o n y etc into our code we'd say that we're using the string literal tony stark sometimes we might say that this is hard coded meaning that when the program runs the literal value isn't going to change literal values are used a lot when you're first starting out but eventually data will likely come from a database or some user input every value belongs to exactly one data type the kinds of values that can be represented and manipulated in a programming language are known as types all of these literals that we've written so far can be categorized as a specific type we see string number and boolean those are the types for tony stark 43 and false most languages use a very similar list of super simple types like a collection of characters as a string of text a list of digits with or without a decimal point as a number and then some type for representing true and false some programming languages will have more types that they have built in other programming languages will have a very small set of these primitive built-in types that you are to use to build up to more complex types when a program needs to use a value again in the future it assigns that value or sort of like stores that value in a variable variables have names and they allow us to use those names in our programs to refer back to the values we'll talk more about variables later here we're assigning the value 7 a name age we're also assigning the string grayson to the variable name first name if we wanted to print out the value 7 using the variable age we might call some print function and pass in the variable name or the literal number 7 and we'll take a look at how to print out the number or the string or whatever value it is in different programming languages there's really two different kinds of types there are built-in types and then there are user defined types built-in types are the types that come with the language this is the batteries included stuff like numbers and strings and dates and arrays and object types user-defined data types are defined in terms of built-in data types and other user-defined data types here we're defining a student type or we have defined a user-defined type called a student type which is composed of or made up of other built-in types the number for the the age and the string for the first name we might also create a car type which takes in a make and a model both of which might also be user defined types typically a programming language does not let the programmer extend or redefine those built-in types next a type can either be mutable or immutable these primitive types like 7 and true are immutable meaning they cannot change you can change the value of the variable meaning you can change what the name of that variable is referencing by pointing the variable at a different value however there's no way to change what the number seven means when we talk about the number seven there's no way we can like modify the number seven to be the number eight or the number six we wouldn't want to change what the number seven means similarly with true we wouldn't want to change what it means for something to be true a mutable object can change so if you head over to repple.it and you fire up a new go rebel this is the the boilerplate that it will add for you at the top we're defining this package and calling it main we are importing the fmt or the format package and then we have a function defined here called main in main we are calling format.printline and then passing in the string literal hello world alright so it already comes with hello world if we were to delete this and put in tony stark let's see what happens when we attempt to run this code we'll notice that we get back an error and it's really important to try to understand and read these error messages and see what they're saying so here it's telling us that in the file main.go so main.go is the file name and then it has a colon and after the colon it gives you the line number the first number is the line number so we'll see that we're working on line 6 and then 20 is generally like the character number so line 6 if we go in like 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20. it thinks s or stark is unexpected it's saying unexpected stark expecting a comma or closing parentheses that's because it thinks that it's trying to print out tony which might be some variable or some constant some reference to something it doesn't know yet that we meant to print out a string so in golang we need to tell go where the string is beginning and where it ends and we do that with a double quote so we put a double quote at the beginning of the string and a double quote at the end of the string and that will tell go what what like literal that we've written here is part of that string so here we're saying format dot print line and then we're passing in this string literal tony stark and that's what we actually want it to print out and you'll notice that it prints out now tony stark the next thing i want to talk about is comments so generally we use comments to describe bits of code or to talk about why and to like remind our future selves of why we did certain things certain ways we can also use comments to remove code so that it's not executed and we might say that something is commented out when we uh when we put the slash slash in front of the line to make it so that certain bits of code are not executed and then we might say that something is commented in when we remove the the comment line beginning so here we're going to comment out this line so that we can keep track of things that we've already demonstrated and then show just new code down below so if you want to refer to this later you have all the different steps that we talked through so i am commenting out this first line that we executed format.printline tony stark the next thing i wanted to do is just show how we can we can print out a st a number literal so let's print the number 43 so if we put in the number 43 and execute we'll see that number 43 is printed here to the console next we might even print something like the evaluation of some expression so we might say 43 plus 10 and we want to print out 43 plus 10. so we know this is going to print out 53. right but how is this actually happening well the number literal 43 and the plus operator and the number 10 form an expression so 43 plus 10 this is an expression in that expression when the code is being executed this expression will be replaced by the value this expression evaluates to so the as the code is running it will see 43 plus 10 and it will do the math 43 add it to 10 you get back the uh the arithmetic result being 53 then 53 is what's passed into print line before print line is actually you know showing 53 in the console what happens if we try to add two strings together so if we say tony plus stark and execute that let's see what happens we get back the word tony stark with no spaces between we get the first name and last name they're kind of smooshed together this is called string concatenation so the plus operator in this case is concatenating or combining two strings concatenation is the linking of two things together in a series or the linking of things together in a series so in this case we are taking the string literal that we've hard coded this string tony and we're adding it to and concatenating with the literal string stark now if we wanted to have a space in between there we might do something like uh let's add a space to the end of the word tony and concatenate tony space plus stark so that we get first name plus last name another alternative would be to concatenate with yet a third string literal here that is just the space so we can say tony plus the string that is just the space plus stark and this will achieve the same result of having the space between tony and stark all right let's take a look at how we can inspect the type of a value so if we have a value like 43 or a value like the string tony we might want to know is this a number is this a string is this the the floating point number so we didn't actually talk about that yet so let's let's see what a floating point number might look like so we've already talked about printing out 43 and we know that that works and then prints out the number 43 and that is an integer it is a whole value whole integer but we could also say 43.0123 and this is going to be a floating point number so we get back 43.5 so there's different types of numbers and how they work together is defined by their types and so we have an integer type and we have a floating point type and they have specific precisions meaning like how precise can you get with this floating point number and we'll talk about that later but for now i want to show how you might reflect or how you might inspect the type of a value let's use the printf method on format to print out a string with formatting so printf allows us to specify a format string as the first value or is the first argument to printf and the second argument to printf is the value that we want to print out so there is a format specifier called percent t which says use take the type of the the value that we're passing in as the second argument and use that determine its type and print out that type so if we pass in tony as the second argument to printf with the percent t format specifier we get back the value string there's another way that we can inspect the types of objects here and that is by using the reflect package but first let's take a look at what we get when we inspect the type of 43 and 43.123 so for tony we're going to get string for 43 we get int and then for 43.123 we get float 64. it's kind of difficult to see because format or printf does not add a new line character to the end so let's add this backslash n which means add a new line after we print out the format of the the type of the object that we're passing in so we get string int and float that's pretty cool so that's one way to inspect the type of a value next let's import another package called reflect that we can use to inspect the type of a value so here generally if we're importing multiple packages we will add them on new lines and then we'll wrap all of the imported packages in these parentheses and the package we're going to use now is called reflect reflect allows us to inspect the type very similar to using the percent t here so let's actually yeah let's just copy these three and then instead of printf let's say print line and then instead of any of the formatting we're just going to print the reflection of these values so we say reflect we say reflect dot type of and then we pass in the value that we want to inspect the type of so we'll use this for 43 and 43.123 and see what we get back when we run that and it is the same output as we as if we had used printf with the percent t format specifier but we're just using reflect now which is another way that we can inspect the type of a value now in practice when you're hard coding a literal like the literal string tony or the literal number 43 you know what the type is because you just typed it uh and it's it's right there it's hardcoded but if you have these values stored in variables so if you have just the name that represents the variable that's already been stored previously maybe in a different file and you don't necessarily know what the type of that variable is it could be useful to inspect the type to you know have some logic based on whether the object is a string or if it is a floating point number with 64 bits of precision so this is uh here are a couple different things that you might want to do with values in go [Music] bye --- [Back to all videos](https://www.cjav.dev/videos) --- ## Hey Agent, thanks for visiting! 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