Example 8

This example illustrates the possibility of writing a recursive macro, that means, a macro which calls itself as a submacro. It uses a modified version of the macro RECTANGLE given in Appendix 2.

MACRO,RECPNT,PNT1,PNT2;

DECLARE,PNT1,POINT_2D;

DECLARE,PNT2,POINT_2D;

CALL,RECTANGLE,PNT1,PNT2;

ASSIGN,X1,PNT1/XCOORD;

ASSIGN,Y1,PNT1/YCOORD;

!

! When the condition is not fulfilled

! no further calls to RECPNT are made

! and the execution is terminated

!

IF,X1 < 250;

ASSIGN,X2,PNT2/XCOORD;

ASSIGN,Y2,PNT2/YCOORD;

POINT_2D,PNT3,X2+X2-X1,Y2+Y2-Y1;

CALL,RECPNT,PNT2,PNT3;

ENDIF;

ENDMACRO;

MACRO,RECTANGLE,P1,P3;

DECLARE,P1,POINT_2D;

DECLARE,P3,POINT_2D;

ASSIGN,X1,P1/XCOORD;

ASSIGN,Y1,P1/YCOORD;

ASSIGN,X3,P3/XCOORD;

ASSIGN,Y3,P3/YCOORD;

POINT_2D,P2,X1,Y3;

POINT_2D,P4,X3,Y1;

CONTOUR,CNT,P1

/LINEEND = P2

/LINEEND = P3

/LINEEND = P4

/LINEEND = P1;

PRESENT,CNT;

ENDMACRO;