Denso BHT-BASIC 100 SERIES, Руководство программиста, Страница: 223 / 577

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Description:
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Creating a user-defined function
FUNCTION ... END FUNCTION creates a user-defined function. The function defini-
tion block between FUNCTION and END FUNCTION is a set of some statements
and functions.
• You cannot make double definition to a same function name.
• This statement block should not be defined in the block-structured statements
( DEF FN
...
END DEF , FOR
...
NEXT , FUNCTION
...
END FUNCTION , IF
...
THEN
...
ELSE
...
END IF , SELECT
...
CASE
...
END SELECT , SUB
...
END SUB and
WHILE
...
WEND ), in the error-handling routine, event-handling routine, or in the
subroutines.
• FUNCTION ... END FUNCTION functions can be recursive.
• In defining a string function, you can specify the maximum stringlength . If
its specification is omitted, the default value of 40 characters takes effect.
• dummyparameter , which corresponds to the variable having the same name in
the function definition block, is a local variable valid only in that block. Therefore,
if a variable having the same name as
dummyparameter is used outside
FUNCTION ... END FUNCTION statement block or used as a dummyparame-
ter of any other function in the same program, then it will be independently
treated.
• In user-defined functions, you can call other user-defined functions. You can nest
FUNCTION
...
END FUNCTION
statements to a maximum of 10 levels.
• When using the FUNCTION ... END FUNCTION together with block-structured
statements ( DEF FN
...
END DEF , FOR
...
NEXT , FUNCTION
...
END FUNCTION ,
IF
…
THEN
...
ELSE
...
END IF , SELECT
...
CASE
...
END SELECT , SUB
...
END SUB
and WHILE
...
WEND ), you can nest them to a maximum of 30 levels.
• If variables other than dummyparameter (s) are specified in the function defini-
tion block, they will be treated as local variables whose current values are avail-
able only in that function definition block, unless
PRIVATE or GLOBAL is
specified.
• EXIT FUNCTION exits the function block prematurely and returns control to the
position immediately after the statement that called the user-defined function.
• Using Syntax 5 allows you to assign a return value for a user-defined function.
The type of
funcname
should match that of a return value. If no return value is
assigned to
funcname
, then the value 0 or a null string will be returned for a
numeric function or a string function, respectively.
■
Calling a user-defined function
funcname calls the function.
• The number of realparameter s should be equal to that of dummyparame-
ter s, and the types of the corresponding variables used in those parameters
should be identical.