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v3:subroutines [2022/01/21 22:18] – [Local and global variables] shawn | v3:subroutines [2024/07/30 22:43] (current) – [Overloading] neils | ||
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While you can use the [[GOSUB]] command in pair with [[RETURN]] to call parts of code as subroutines, | While you can use the [[GOSUB]] command in pair with [[RETURN]] to call parts of code as subroutines, | ||
- | ===== Defining | + | ===== Defining |
Subroutines are named routines that accept zero or more arguments. The simplest syntax to define a subroutine is the following: | Subroutines are named routines that accept zero or more arguments. The simplest syntax to define a subroutine is the following: | ||
- | SUB < | + | SUB < |
< | < | ||
END SUB | END SUB | ||
- | It is worth noting that a subroutine does not require arguments. In this case you still must add the empty parentheses after the routine name, though, like so: | + | It is worth noting that the argument list is optional. If you omit the arguments, |
SUB < | SUB < | ||
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END SUB | END SUB | ||
- | ===== Calling | + | ===== Calling |
You can use the [[CALL]] keyword to call a subroutine. It behaves similarly to [[GOSUB]] with an important difference: '' | You can use the [[CALL]] keyword to call a subroutine. It behaves similarly to [[GOSUB]] with an important difference: '' | ||
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END SUB | END SUB | ||
| | ||
- | CALL greet(" | + | CALL greet(" |
- | CALL greet(" | + | CALL greet(" |
The '' | The '' | ||
- | ===== Exiting | + | ===== Exiting |
The subroutine will be exited at the '' | The subroutine will be exited at the '' | ||
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==== Shadowing ==== | ==== Shadowing ==== | ||
- | A local variable may have the same name as a global variable. In such cases the local variable will be used inside the subroutine. Consider the following example: | + | A local variable may have the same name as a global variable. In such cases the local variable will be used inside the subroutine. |
a = 42 | a = 42 | ||
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</ | </ | ||
- | ==== Static | + | ==== Static |
You can mix static and dynamic behaviour using the '' | You can mix static and dynamic behaviour using the '' | ||
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===== Overloading ===== | ===== Overloading ===== | ||
- | When passing arguments to a subroutine, the compiler will match the number of arguments | + | Subroutine overloading, commonly known as method overloading |
- | If the number | + | Overloaded subroutines have the same name but differ in the type, number, |
- | But what if the programmer desires a subroutine that behaves differently depending on the number or type of arguments that are passed? This is possible using overloading. A subroutine may have as many variations as desired. If there is more than one variation, the compiler will locate the best match among the candidates for the call. Consider the following example: | + | ==== Compile-Time Polymorphism ==== |
- | | + | The appropriate subroutine to call is determined at compile-time based on the arguments provided in the call. |
- | PRINT "a is an integer: "; a | + | |
+ | Consider the following example: | ||
+ | |||
+ | | ||
+ | PRINT msg | ||
END SUB | END SUB | ||
| | ||
- | SUB test (a AS STRING * 16) OVERLOAD | + | SUB PrintMessage(msg AS STRING * 16, num AS INT) OVERLOAD |
- | PRINT "a is a string: | + | PRINT msg; " "; |
END SUB | END SUB | ||
| | ||
- | CALL test(5) | + | CALL PrintMessage(" |
- | CALL test("hello") | + | CALL PrintMessage("The number is", 42) |
<adm warning> | <adm warning> |