Denso BHT-BASIC 100 SERIES, Programmer'S Manual

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Description:
■
Creating a user-defined function
DEF FN creates a user-defined function.
• 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.
• The
DEF FN
statement 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.
• DEF FN functions cannot be recursive.
• The type of functionname should match that of the function definition
expression .
• In defining a string function, you can specify the maximum stringlength for a
return value. 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 expression , is a local variable valid only in that
expression . Therefore, if a variable having the same name as dummypa-
rameter is used outside DEF FN statement or used as a dummyparameter
of any other function in the same program, then it will be independently treated.
• expression describes some operations for the user-defined function. It
should be within one program line including definition described left to the equal
sign (=).
• expression can call other user-defined functions. You can nest DEF FN state-
ments to a maximum of 10 levels.
• If variables other than
dummyparameter
(s) are specified in
expression
,
they will be treated as global variables whose current values are available.
• stringlength should be enclosed with a pair of square brackets [ ].
■
Calling a user-defined function
FNfunctionname
calls a user-defined 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.
• If you specify a global variable in
realparameter
when calling a user-defined
function, the user-defined function cannot update the value of the global variable.
This is because all realparameter s are passed not by address but by value.
(So called "Call-by-value")