66 lines
1.2 KiB
Markdown
66 lines
1.2 KiB
Markdown
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# Subroutines
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Sometimes in Granite, you will need to be able to call subroutines (a kind of function) instead of jumping and be able to _return_ to where you were before. This is possible!
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## New operations
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* `:#`, stack push, pushes the current location to the stack, allowing a return
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* `:|`, return, returns back to the previous pushed location, crashes if no location pushed
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## Tutorial
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Look at this program:
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```
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:?x
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:&x,temp
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:=default,temp,0
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:@print
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:^x
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:!x
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:~
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:@default
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:>10,x
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:<print
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```
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This program will take a number, add 1 to it and print it out, but default to 10 if a string is passed in.
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A more nicer way to do this could be with subroutines!
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First, move the default label and its two operations above the prompt and define an entry label above the prompt but below the default label like this:
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```
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:<entry
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:@default
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:>10,x
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:<print
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:@entry
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:?x
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:&x,temp
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:=default,temp,0
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:^x
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:!x
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```
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Now before the conditional jump to default after the type check, add a `:#` operation and replace the `:<print` operation with `:|`
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The program now functions the same, but looks much more neater with subroutines!
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## After example
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```
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:<entry
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:@default
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:>10,x
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:|
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:@entry
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:?x
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:&x,temp
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:#
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:=default,temp,0
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:^x
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:!x
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```
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