Topic       : The GFA-Basic Compendium
Author      : GFA Systemtechnik GmbH
Version     : GFABasic.HYP v2.98 (12/31/2023)
Subject     : Documentation/Programming
Nodes       : 899
Index Size  : 28056
HCP-Version : 3
Compiled on : Atari
@charset    : atarist
@lang       : 
@default    : Document not found
@help       : Help
@options    : +g -i -s +z
@width      : 75
@hostname   : STRNGSRV
@hostname   : CAB     
@hostname   : HIGHWIRE
@hostname   : THING   
View Ref-FileTips on porting 'C' to GFABASIC

C         GFA        Notes
-------------------------------
&&        AND        IF compare
||        OR         IF compare
!=        <>         IF compare
==        =          IF compare
&         AND()      operator
|         OR()       operator
%         MOD()      operator
!         NOT        operator
~         NOT        bitwise
^         XOR        bitwise
<<        SHL()      bitwise
>>        SHR()      bitwise
var++     INC var
var--     DEC var
a+=b      a=a+b
a-=b      a=a-b
a*=b      a=a*b
a/=b      a=a/b
a%=b      a=MOD(a,b)
a&=b      a=AND(a,b)
a|=b      a=OR(a,b)
a^=b      a=XOR(a,b)
a<<=b     a=SHL(a,b)
a>>=b     a=SHR(a,b)
var[x]    array(x)   subscript
&var      *var       address of
Random()  XBIOS(17)  24-bit random number


These are structure referenece and must be recoded.

a->b  structure dereference
a.b   structure reference


Variable types:

int var         word size
unsigned int    card size (must use long)
char var        string or byte size
int var[10]     DIM var&(10)
#define var 2   replaced at compile time


Constructs like this do not work in GFA:
  a=b=c=2

  In 'C' this sets all variables to the value of 2.
  GFA interprets this as a logic comparison and it must be recoded:
    a=2
    b=2  !assigned individually
    c=2


The ? ... : ... operator

The ? ... : ... operator is a sort of shorthand if...else... statement.
Because it is a little cryptic, it is not often used, but the basic form is as
follows:

(condition) ?  expression1 : expression2;

The program evaluates condition. If it is true (not zero), then expression1 is
returned; otherwise, expression2 is returned.

For example, in the short program below, the line
bas = (foo > bar) ? foo : bar;
assigns foo to bas if foo is greater than bar; otherwise, it assigns bar to
bas.

#include <stdio.h>

int main()
{
  int foo = 10;
  int bar = 50;
  int bas;

  bas = (foo > bar) ? foo : bar;

  printf("bas = %d\n\n", bas);

  return 0;
}

The program will print bas = 50 as a result.

Another example:
  x = (x>0) ? x : -x

  translates to:

  IF x>0
    x=x
  ELSE
    x=-x
  ENDIF

  which basically is the same as x=ABS(x)