Function prototype: Difference between revisions
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A routine may make a named parameter mandatory using exclamation mark. (This is more useful in multi subs than in stubs though.) |
A routine may make a named parameter mandatory using exclamation mark. (This is more useful in multi subs than in stubs though.) |
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<lang perl6>sub foo ($, :$option! --> Int) {...}</lang> |
<lang perl6>sub foo ($, :$option! --> Int) {...}</lang> |
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=={{header|Racket}}== |
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Most of the points are covered in this program |
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<lang Racket>#lang racket |
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(define (no-arg) (void)) |
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(define (two-args a b) (void)) ;arguments are always named |
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(define (varargs . args) (void)) ;the extra arguments are stored in a list |
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(define (varargs2 a . args) (void)) ;one obligatory argument and the rest are contained in the list |
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(define (optional-arg (a 5)) (void)) ;a defaults to 5</lang> |
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(void) is a function that returns nothing, so this are prototypes that do nothing. |
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Although standard Racket doesn't allow type declarations, it allows contracts, so we can add this to the previous declarations |
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<lang Racket>(provide (contract-out |
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[two-args (integer? integer? . -> . any)]))</lang> |
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then any module that imports the function can only pass integers to two-args. |
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Another way is using the typed/racket language, like this |
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<lang Racket>#lang typed/racket |
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(: two-args (Integer Integer -> Any)) |
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(define (two-args a b) (void))</lang> |
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{{omit from|AutoHotkey}} |
{{omit from|AutoHotkey}} |
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