[PPL-devel] Bug in ppl_new_LinExpression_with_dimension

[Pedro Vasconcelos]

While experimenting with the Haskell PPL binding, I noticed that the C
interface function "ppl_new_LinExpression_with_dimension" always creates
an expression with one plus the specified dimension. The following code
illustrates the problem: 

#include <ppl_c.h>

main () {
  ppl_LinExpression_t e;
  ppl_dimension_type dim_in=3, dim_out;;

  ppl_initialize();

  ppl_new_LinExpression_with_dimension(&e, dim_in);
  dim_out = ppl_LinExpression_space_dimension(e);
  printf("%d, %d\n", dim_in, dim_out);    /* 3, 4 rather than 3,3 as expected */

  ppl_finalize();
}

Looking at the source code interface/C/ppl_c.cc, it becomes clear that
the expression created has a single Variable(d), therefore dimension d+1:

int
ppl_new_LinExpression_with_dimension(ppl_LinExpression_t* ple,
				     ppl_dimension_type d) try {
  *ple = to_nonconst(new LinExpression(0*Variable(d)));  /* <----- should be Variable(d-1) */
  return 0;
}
CATCH_ALL

This is of course trivial to correct, but I thought it best to report so
that it gets corrected in the newer releases.

Best regards,

Pedro