Denso BHT-BASIC 100 SERIES, Руководство программиста

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5.3 User-defined Functions
Out of user-defined functions, the
SUB
and
FUNCTION
functions can be called from other
files. The DEF FN function can be called only in the file where that function is defined and
should start with an FN .
The DEF FN and FUNCTION functions are classified into three types: integer functions, real
functions, and character functions, each of which should be defined in the following format:
■
Setting Character String Length of Returned Values of Character Functions
A character function may return 1 through 255 characters. Note that the default character
string length results in the returned value of 40 characters.
If the returned value of the character string length is always less than 40 characters, you can
use the stack efficiently by setting the actual required value smaller than the default as the
maximum length. This is because the Interpreter positions returned values on the stack during
execution of user-defined functions so as to occupy the memory area by the maximum length
size. To define a function which results in the returned value of one character, for example,
describe as follows:
DEF FNshort$(i%)[1]
On the other hand, if the returned value is more than 40 characters, it is necessary to set the
actually required length. To define a function which results in the returned values of 128 char-
acters, for example, describe as follows:
DEF FNlong$(i%)[128]
■ Dummy Arguments and Real Arguments
Dummy arguments are used for defining user-defined functions. In the example below, i% is a
dummy argument.
DEF FNfunc%(i%)
FNfunc%=i%*5
END DEF
Real arguments are actually passed to user-defined functions when those functions are called.
In the example below, 3 is a real argument.
PRINT FNfunc%(3)
User-defined Function Format of DEF FN Format of FUNCTION
Integer functions
FN functionname %
Real functions
FN functionname
Character functions
FN functionname $