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53 lines
1.7 KiB
Markdown
53 lines
1.7 KiB
Markdown
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A BASIC **function** is a procedure that returns one value in it's name. A function can be used as a statement [argument](argument) or be assigned to a [variable](variable).
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User-defined functions are possible and behave the same way, with the only exception that user-defined functions cannot currently have optional [argument](argument)s.
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Altering the variables that are used as arguments within the function will cause the same changes to the variables outside of the function. This also applies to [Sub (explanatory)](Sub-(explanatory)). Variables that are not arguments of the function will not be changed if used within the function unless they are [SHARED](SHARED). See the second example of [sub (explanatory)](sub-(explanatory)) for a demonstration of this (it functions the same way in subs).
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The arguments of a function need to be enclosed with parantheses (unless there are no arguments).
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Function and [Sub (explanatory)](Sub-(explanatory)) procedures are placed after the main code body.
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## Example(s)
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Some BASIC functions.
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```vb
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a = ABS(-1)
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b = INT(2.54)
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c = CINT(2.54)
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PRINT "ABS(-1) gives"; a
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PRINT "INT(2.54) gives"; b
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PRINT "CINT(2.54) gives"; c
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PRINT "ATN(1) * 4 gives"; ATN(1) * 4
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```
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User-defined function.
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```vb
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d = dividebyhalf(4)
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PRINT "dividebyhalf(4) gives"; d
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FUNCTION dividebyhalf (number)
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IF number <> 0 THEN
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half = number / 2
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ELSE
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half = 0
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END IF
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dividebyhalf = half
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END FUNCTION
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```
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> *Explanation:* The calculated value is assigned to the name of the function. When calculations require several changes, use an intermediary variable. Then assign that value to the function name.
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## See Also
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* [SUB](SUB). [FUNCTION](FUNCTION)
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* [Statement](Statement), [Sub (explanatory)](Sub-(explanatory))
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* [Argument](Argument)
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