Cross-calling Basic and C Procedures

It is possible to call BASIC subs and functions from C and C functions from BASIC. I will refer to this as "cross-calling".

Since Tibbo BASIC arrays and structures are not compatible with arrays and structures of Tibbo C, it is not possible to cross-call procedures that have array or structure arguments or return the same.

note_warning-wt There is no cross-checking of argument and return value types. You could define f as a word argument in the BASIC declaration, while having it as a string type in the C implementation, or vice versa. TIDE will not be able to catch such a discrepancy. Be very careful with this!

The following table will help you with cross-calling: it puts together corresponding language elements of Tibbo BASIC and C:

Tibbo BASIC

Tibbo C

Subs and functions

sub name()

end sub

void name(){

}

function name() as simple_type

end function

simple_type name(){

}

Argument passing:

sub name(x as simple_type)...

void name(simple_type x)...

sub name(ByVal x as simple_type)...

void name(simple_type x)...

sub name(ByRef x as simple_type)

void name(simple_type *x)...

Here is an example of calling two C functions from BASIC:

** Tibbo Basic **

declare function c_increment(x as byte) as byte
declare sub c_str_double(byref s as string) 'notice how byref becomes * on C side

sub on_sys_init
   dim x as byte=5
   x=c_increment(x) 'x will be 6

   dim s as string="TIBBO"
   c_str_double(s) 's will be "TIBBOTIBBO"
end sub

** Tibbo C **

unsigned char c_increment(unsigned char x){
   return ++x;
}

void c_str_double(string *s){
   *s=*s+*s;
}

The same, but the other way around — C calls a function and a sub in BASIC:

** Tibbo Basic **

function basic_increment(x as byte) as byte 
   basic_increment=x+1
end function

sub basic_str_double(byref s as string)
   s=s+s
end sub

** Tibbo C **

unsigned char basic_increment(unsigned char x);
void basic_str_double(string *s);

void on_sys_init(){
   unsigned char x=5;
   x=basic_increment(x);

   string s="TIBBO";
   basic_str_double(&s);
}