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(g-wrap.info)Printing object representations

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Printing object representations
===============================

The function for printing a representation of the object should have a
declaration similar to this:
     void PRINT_FN_NAME (TYPE* obj, GWSCM port, int writingp);
The first parameter accepts a pointer to the object to be printed, the
second parameter accepts a Scheme value representing the Scheme port to
write to, and the final argument indicates whether the object is being
printed with `display' (`writingp==0') or `write' (`writingp!=0').  The
function `gw_puts(char*,GWSCM)' can be used to write a string to the
port.

Here is an example of a function used for printing a matrix type:
     void MAT_print(MAT *m, GWSCM scmport, int writingp) {
       int i, j;
       char buff[80];
     
       if ( !m ) {  gw_puts("MNULL",scmport); return; }
       if ( writingp ) {
         sprintf(buff,"(MAT %d %d (", m->m, m->n);
         gw_puts(buff, scmport);
       } else {
         gw_puts("\n", scmport);
       }
       for ( i = 0; i < m->m; i++ ) {
         if ( !writingp ) { gw_puts("[ ", scmport); }
         for ( j = 0; j < m->n; j++ ) {
           sprintf(buff,"%lf ", m->me[i][j]);
           gw_puts(buff, scmport);
         }
         if ( !writingp ) { gw_puts("]\n", scmport); }
       }
       if ( writingp ) { gw_puts(")) ", scmport); }
     }