51 lines
2 KiB
Markdown
51 lines
2 KiB
Markdown
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# Manipulating values
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Granite does not allow you to modify literals directly, instead requiring you to use bindings to variables and modifying them within bindings, keeping all values tracked and stored.
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## New operations
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* `:>(value),(variable)`, set variable, Stores `(value)` into `(variable)`
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* `:^(variable)`, increment, if `(variable)` is a number, add one to it.
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* `:v(variable)`, decrement, if `(variable)` is a number, remove one from it.
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* `:!(variable)`, print, outputs the value in `(variable)`
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## Tutorial
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To begin your program, make a new file called `counter.granite`. This will be the source code of your program!
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Throughout this guidebook, we will be creating a program which is able to count up from a starting number to a final number by a certain step each time! To do this, we first need to learn the basics of value manipulation.
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In your program's source place these two statements in:
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```
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:>0,starting_number
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:!starting_number
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```
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These two statements will simply create (initialise) the `starting_number` variable with the value 0 and print it to the screen!
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Now run your program with the Granite runtime. There are two ways to do this:
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* If you have installed Granite to your path, type `granite -i counter.granite`.
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* If you are in your local clone of the Granite runtime repository, type `cargo run -- -i counter.granite`.
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You should now see the program run and output 0!
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If the program does _not_ run and gives you an error, make sure your source code matches the above example _exactly_. The Granite language does not like having spaces between variables and commas, and will fail if you add spaces.
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Next, we want to _manipulate_ the value. We can do this by using the `:^(variable)` operation!
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Make your program's source code look like _this_ now:
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```
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:>0,starting_number
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:^starting_number
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:!starting_number
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```
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Now run your program, you should see the number 1!
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## Extension
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Try using the _decrement_ operation (`:v(variable)`) to make the output a negative number!
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## Continue the guidebook
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* [Next page: Jumps and labels](jumps-labels.md)
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