granite-docs/docs/type-checking.md

Type checking

Granite contains two types: integers and strings, and due to how some operations work it may be worth type checking these explicitly within the code.

New operations

• :&(variable),(output), type check, if (variable) is an integer then set (output) to 1 otherwise set (output) to 0

Tutorial

Look at this simple program:

:?x
:^x
:!x

This program simply asks the user for a number and adds 1 to it.

This program works fine provided the user inputs a number.

? 50
51

But things begin to fall apart if the user does not input an integer.

? I'm an evil string! >:)
Non-number variable x on increment.

Type checking can solve this problem by allowing the programmer to safely recover when an invalid type is detected.

Firstly, we want to make the question a label so make a label called question above :?x.

Also add a variable drop after the question label but before asking the user for x.

Now directly after :?x but before :^x we want to add the type check operation so add :&x,type after :?x.

Now we will have an integer corresponding to whether x is an integer or not. So now after :&x,type you can add a conditional jump that jumps to the question label if type is equal to 0 which means that the user inputted a string.

Now our program is immune to strings messing things up:

? I'm an evil string! >:)
? No strings? :(
? 10
11

Extension

Can you prompt the user to input an integer after incorrectly putting in a string?

After example

:@question
:$x
:?x
:&x,type
:=question,type,0
:^x
:!x