[eclipse-clp-users] compiler leaves spurious choice points

Dear all,

sometimes, the compiler leaves spurious choice points, i.e., choice points
that are later discovered to be not there.  I thought (or hoped) that these
"false" choice points would be eliminated by optimization via type testing.

Is there any way to prevent this?  It is somewhat distracting during tracing
and bug fixing.

Best regards,

Ulrich



An example:

--- ttt.ecl ---
t2(T1, _T2) :-
    free(T1),
    !,
    writeln(a).

t2(_T1, T2) :-
    T2 \== [],
    writeln(b).

t2(_T1, []) :-
    writeln(c).
----------------

scholz_at_...290...:~/Forschung/Invarianten/Version_2010_12_09$ eclipse
ECLiPSe Constraint Logic Programming System [kernel]
Kernel and basic libraries copyright Cisco Systems, Inc.
and subject to the Cisco-style Mozilla Public Licence 1.1
(see legal/cmpl.txt or www.eclipse-clp.org/licence)
Source available at www.sourceforge.org/projects/eclipse-clp
GMP library copyright Free Software Foundation, see legal/lgpl.txt
For other libraries see their individual copyright notices
Version 6.0 #154 (i386_linux), Fri Jul 16 06:11 2010
[eclipse 4]: [ttt].
source_processor.eco loaded in 0.00 seconds
hash.eco   loaded in 0.01 seconds
compiler_common.eco loaded in 0.02 seconds
compiler_normalise.eco loaded in 0.00 seconds
compiler_map.eco loaded in 0.00 seconds
compiler_analysis.eco loaded in 0.00 seconds
compiler_peephole.eco loaded in 0.01 seconds
compiler_codegen.eco loaded in 0.01 seconds
compiler_varclass.eco loaded in 0.00 seconds
compiler_indexing.eco loaded in 0.01 seconds
compiler_regassign.eco loaded in 0.01 seconds
asm.eco    loaded in 0.01 seconds
module_options.eco loaded in 0.00 seconds
ecl_compiler.eco loaded in 0.08 seconds
ttt.ecl    compiled 412 bytes in 0.00 seconds

Yes (0.08s cpu)
[eclipse 5]: t2(y,z).
b

Yes (0.00s cpu, solution 1, maybe more) ? ;

No (0.00s cpu)
[eclipse 6]: