Denso BHT-BASIC 100 SERIES, Programmer'S Manual

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199
Description:
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Creating a user-defined function
DEF FN
...
END DEF creates a user-defined function. The function definition block
between DEF FN and END DEF is a set of some statements and functions.
• Definition of a user-defined function should appear preceding a calling statement
of the user-defined function in a source program.
• 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 subrou-
tines.
• DEF FN
...
END DEF 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 DEF
FN
...
END DEF statement block or used as a dummyparameter 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
DEF FN
...
END DEF statements to a maximum of 10 levels.
• When using the DEF FN
...
END DEF 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 global variables whose current values are avail-
able.
• EXIT DEF exits the function block prematurely and returns control to the position
immediately after the statement that called the user-defined function.
• The block-format DEF FN statement should be followed by END DEF which ends
the function block and returns control to the position immediately after the state-
ment that called the user-defined function.
• Using Syntax 5 allows you to assign a return value for a user-defined function.
The type of
functionname
should match that of a return value. If no return
value is assigned to functionname , then the value 0 or a null string will be
returned for a numeric function or a string function, respectively.