DisjConditions.pm

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Author : Stefano Lattarini
Date : 2012-03-04 15:44:46
Hash : 7df05a0b
Message : maint: require perl 5.6 throughout That version of perl is quite old already, so it should be OK to require it. More importantly, it is the older perl versions the developers can currently use for testing, thus it's safer and more honest to just require it throughout. And anyway, we were already requiring it in Automake::Getopt, which implied that both automake and aclocal wouldn't have worked in practice with an older perl version. See also the discussion related to automake bug#10925. * lib/Automake/ChannelDefs.pm: Adjusted to require perl 5.6. * lib/Automake/Channels.pm: Likewise. * lib/Automake/Condition.pm: Likewise. * lib/Automake/Configure_ac.pm: Likewise. * lib/Automake/DisjConditions.pm: Likewise. * lib/Automake/FileUtils.pm: Likewise. * lib/Automake/General.pm: Likewise. * lib/Automake/Item.pm: Likewise. * lib/Automake/ItemDef.pm: Likewise. * lib/Automake/Location.pm: Likewise. * lib/Automake/Options.pm: Likewise. * lib/Automake/Rule.pm: Likewise. * lib/Automake/RuleDef.pm: Likewise. * lib/Automake/Struct.pm: Likewise. * lib/Automake/VarDef.pm: Likewise. * lib/Automake/Variable.pm: Likewise. * lib/Automake/Version.pm: Likewise. * lib/Automake/Wrap.pm: Likewise. * lib/Automake/XFile.pm: Likewise.
lib/Automake/DisjConditions.pm
# Copyright (C) 1997-2012 Free Software Foundation, Inc.

# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2, or (at your option)
# any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.

# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

package Automake::DisjConditions;

use 5.006;
use strict;
use Carp;
use Automake::Condition qw/TRUE FALSE/;

=head1 NAME

Automake::DisjConditions - record a disjunction of Conditions

=head1 SYNOPSIS

  use Automake::Condition;
  use Automake::DisjConditions;

  # Create a Condition to represent "COND1 and not COND2".
  my $cond = new Automake::Condition "COND1_TRUE", "COND2_FALSE";
  # Create a Condition to represent "not COND3".
  my $other = new Automake::Condition "COND3_FALSE";

  # Create a DisjConditions to represent
  #   "(COND1 and not COND2) or (not COND3)"
  my $set = new Automake::DisjConditions $cond, $other;

  # Return the list of Conditions involved in $set.
  my @conds = $set->conds;

  # Return one of the Condition involved in $set.
  my $cond = $set->one_cond;

  # Return true iff $set is always true (i.e. its subconditions
  # cover all cases).
  if ($set->true) { ... }

  # Return false iff $set is always false (i.e. is empty, or contains
  # only false conditions).
  if ($set->false) { ... }

  # Return a string representing the DisjConditions.
  #   "COND1_TRUE COND2_FALSE | COND3_FALSE"
  my $str = $set->string;

  # Return a human readable string representing the DisjConditions.
  #   "(COND1 and !COND2) or (!COND3)"
  my $str = $set->human;

  # Merge (OR) several DisjConditions.
  my $all = $set->merge($set2, $set3, ...)

  # Invert a DisjConditions, i.e., create a new DisjConditions
  # that complements $set.
  my $inv = $set->invert;

  # Multiply two DisjConditions.
  my $prod = $set1->multiply ($set2);

  # Return the subconditions of a DisjConditions with respect to
  # a Condition.  See the description for a real example.
  my $subconds = $set->sub_conditions ($cond);

  # Check whether a new definition in condition $cond would be
  # ambiguous w.r.t. existing definitions in $set.
  ($msg, $ambig_cond) = $set->ambiguous_p ($what, $cond);

=head1 DESCRIPTION

A C<DisjConditions> is a disjunction of C<Condition>s.  In Automake
they are used to represent the conditions into which Makefile
variables and Makefile rules are defined.

If the variable C<VAR> is defined as

  if COND1
    if COND2
      VAR = value1
    endif
  endif
  if !COND3
    if COND4
      VAR = value2
    endif
  endif

then it will be associated a C<DisjConditions> created with
the following statement.

  new Automake::DisjConditions
    (new Automake::Condition ("COND1_TRUE", "COND2_TRUE"),
     new Automake::Condition ("COND3_FALSE", "COND4_TRUE"));

As you can see, a C<DisjConditions> is made from a list of
C<Condition>s.  Since C<DisjConditions> is a disjunction, and
C<Condition> is a conjunction, the above can be read as
follows.

  (COND1 and COND2) or ((not COND3) and COND4)

That's indeed the condition in which C<VAR> has a value.

Like C<Condition> objects, a C<DisjConditions> object is unique
with respect to its conditions.  Two C<DisjConditions> objects created
for the same set of conditions will have the same address.  This makes
it easy to compare C<DisjConditions>s: just compare the references.

=head2 Methods

=over 4

=item C<$set = new Automake::DisjConditions [@conds]>

Create a C<DisjConditions> object from the list of C<Condition>
objects passed in arguments.

If the C<@conds> list is empty, the C<DisjConditions> is assumed to be
false.

As explained previously, the reference (object) returned is unique
with respect to C<@conds>.  For this purpose, duplicate elements are
ignored.

=cut

# Keys in this hash are DisjConditions strings. Values are the
# associated object DisjConditions.  This is used by 'new' to reuse
# DisjConditions objects with identical conditions.
use vars '%_disjcondition_singletons';

sub new ($;@)
{
  my ($class, @conds) = @_;
  my @filtered_conds = ();
  for my $cond (@conds)
    {
      confess "'$cond' isn't a reference" unless ref $cond;
      confess "'$cond' isn't an Automake::Condition"
	unless $cond->isa ("Automake::Condition");

      # This is a disjunction of conditions, so we drop
      # false conditions.  We'll always treat an "empty"
      # DisjConditions as false for this reason.
      next if $cond->false;

      push @filtered_conds, $cond;
    }

  my $string;
  if (@filtered_conds)
    {
      @filtered_conds = sort { $a->string cmp $b->string } @filtered_conds;
      $string = join (' | ', map { $_->string } @filtered_conds);
    }
  else
    {
      $string = 'FALSE';
    }

  # Return any existing identical DisjConditions.
  my $me = $_disjcondition_singletons{$string};
  return $me if $me;

  # Else, create a new DisjConditions.

  # Store conditions as keys AND as values, because blessed
  # objects are converted to strings when used as keys (so
  # at least we still have the value when we need to call
  # a method).
  my %h = map {$_ => $_} @filtered_conds;

  my $self = {
    hash => \%h,
    string => $string,
    conds => \@filtered_conds,
  };
  bless $self, $class;

  $_disjcondition_singletons{$string} = $self;
  return $self;
}


=item C<CLONE>

Internal special subroutine to fix up the self hashes in
C<%_disjcondition_singletons> upon thread creation.  C<CLONE> is invoked
automatically with ithreads from Perl 5.7.2 or later, so if you use this
module with earlier versions of Perl, it is not thread-safe.

=cut

sub CLONE
{
  foreach my $self (values %_disjcondition_singletons)
    {
      my %h = map { $_ => $_ } @{$self->{'conds'}};
      $self->{'hash'} = \%h;
    }
}


=item C<@conds = $set-E<gt>conds>

Return the list of C<Condition> objects involved in C<$set>.

=cut

sub conds ($ )
{
  my ($self) = @_;
  return @{$self->{'conds'}};
}

=item C<$cond = $set-E<gt>one_cond>

Return one C<Condition> object involved in C<$set>.

=cut

sub one_cond ($)
{
  my ($self) = @_;
  return (%{$self->{'hash'}},)[1];
}

=item C<$et = $set-E<gt>false>

Return 1 iff the C<DisjConditions> object is always false (i.e., if it
is empty, or if it contains only false C<Condition>s). Return 0
otherwise.

=cut

sub false ($ )
{
  my ($self) = @_;
  return 0 == keys %{$self->{'hash'}};
}

=item C<$et = $set-E<gt>true>

Return 1 iff the C<DisjConditions> object is always true (i.e. covers all
conditions). Return 0 otherwise.

=cut

sub true ($ )
{
  my ($self) = @_;
  return $self->invert->false;
}

=item C<$str = $set-E<gt>string>

Build a string which denotes the C<DisjConditions>.

=cut

sub string ($ )
{
  my ($self) = @_;
  return $self->{'string'};
}

=item C<$cond-E<gt>human>

Build a human readable string which denotes the C<DisjConditions>.

=cut

sub human ($ )
{
  my ($self) = @_;

  return $self->{'human'} if defined $self->{'human'};

  my $res = '';
  if ($self->false)
    {
      $res = 'FALSE';
    }
  else
    {
      my @c = $self->conds;
      if (1 == @c)
	{
	  $res = $c[0]->human;
	}
      else
	{
	  $res = '(' . join (') or (', map { $_->human } $self->conds) . ')';
	}
    }
  $self->{'human'} = $res;
  return $res;
}


=item C<$newcond = $cond-E<gt>merge (@otherconds)>

Return a new C<DisjConditions> which is the disjunction of
C<$cond> and C<@otherconds>.  Items in C<@otherconds> can be
@C<Condition>s or C<DisjConditions>.

=cut

sub merge ($@)
{
  my ($self, @otherconds) = @_;
  new Automake::DisjConditions (
    map { $_->isa ("Automake::DisjConditions") ? $_->conds : $_ }
        ($self, @otherconds));
}


=item C<$prod = $set1-E<gt>multiply ($set2)>

Multiply two conditional sets.

  my $set1 = new Automake::DisjConditions
    (new Automake::Condition ("A_TRUE"),
     new Automake::Condition ("B_TRUE"));
  my $set2 = new Automake::DisjConditions
    (new Automake::Condition ("C_FALSE"),
     new Automake::Condition ("D_FALSE"));

C<$set1-E<gt>multiply ($set2)> will return

  new Automake::DisjConditions
    (new Automake::Condition ("A_TRUE", "C_FALSE"),
     new Automake::Condition ("B_TRUE", "C_FALSE"),;
     new Automake::Condition ("A_TRUE", "D_FALSE"),
     new Automake::Condition ("B_TRUE", "D_FALSE"));

The argument can also be a C<Condition>.

=cut

# Same as multiply() but take a list of Conditionals as second argument.
# We use this in invert().
sub _multiply ($@)
{
  my ($self, @set) = @_;
  my @res = map { $_->multiply (@set) } $self->conds;
  return new Automake::DisjConditions (Automake::Condition::reduce_or @res);
}

sub multiply ($$)
{
  my ($self, $set) = @_;
  return $self->_multiply ($set) if $set->isa('Automake::Condition');
  return $self->_multiply ($set->conds);
}

=item C<$inv = $set-E<gt>invert>

Invert a C<DisjConditions>.  Return a C<DisjConditions> which is true
when C<$set> is false, and vice-versa.

  my $set = new Automake::DisjConditions
    (new Automake::Condition ("A_TRUE", "B_TRUE"),
     new Automake::Condition ("A_FALSE", "B_FALSE"));

Calling C<$set-E<gt>invert> will return the following C<DisjConditions>.

  new Automake::DisjConditions
    (new Automake::Condition ("A_TRUE", "B_FALSE"),
     new Automake::Condition ("A_FALSE", "B_TRUE"));

We implement the inversion by a product-of-sums to sum-of-products
conversion using repeated multiplications.  Because of the way we
implement multiplication, the result of inversion is in canonical
prime implicant form.

=cut

sub invert($ )
{
  my ($self) = @_;

  return $self->{'invert'} if defined $self->{'invert'};

  # The invert of an empty DisjConditions is TRUE.
  my $res = new Automake::DisjConditions TRUE;

  #   !((a.b)+(c.d)+(e.f))
  # = (!a+!b).(!c+!d).(!e+!f)
  # We develop this into a sum of product iteratively, starting from TRUE:
  # 1) TRUE
  # 2) TRUE.!a + TRUE.!b
  # 3) TRUE.!a.!c + TRUE.!b.!c + TRUE.!a.!d + TRUE.!b.!d
  # 4) TRUE.!a.!c.!e + TRUE.!b.!c.!e + TRUE.!a.!d.!e + TRUE.!b.!d.!e
  #    + TRUE.!a.!c.!f + TRUE.!b.!c.!f + TRUE.!a.!d.!f + TRUE.!b.!d.!f
  foreach my $cond ($self->conds)
    {
      $res = $res->_multiply ($cond->not);
    }

  # Cache result.
  $self->{'invert'} = $res;
  # It's tempting to also set $res->{'invert'} to $self, but that
  # is a bad idea as $self hasn't been normalized in any way.
  # (Different inputs can produce the same inverted set.)
  return $res;
}

=item C<$self-E<gt>simplify>

Return a C<Disjunction> which is a simplified canonical form of C<$self>.
This canonical form contains only prime implicants, but it can contain
non-essential prime implicants.

=cut

sub simplify ($)
{
  my ($self) = @_;
  return $self->invert->invert;
}

=item C<$self-E<gt>sub_conditions ($cond)>

Return the subconditions of C<$self> that contains C<$cond>, with
C<$cond> stripped.  More formally, return C<$res> such that
C<$res-E<gt>multiply ($cond) == $self-E<gt>multiply ($cond)> and
C<$res> does not mention any of the variables in C<$cond>.

For instance, consider:

  my $a = new Automake::DisjConditions
    (new Automake::Condition ("A_TRUE", "B_TRUE"),
     new Automake::Condition ("A_TRUE", "C_FALSE"),
     new Automake::Condition ("A_TRUE", "B_FALSE", "C_TRUE"),
     new Automake::Condition ("A_FALSE"));
  my $b = new Automake::DisjConditions
    (new Automake::Condition ("A_TRUE", "B_FALSE"));

Calling C<$a-E<gt>sub_conditions ($b)> will return the following
C<DisjConditions>.

  new Automake::DisjConditions
    (new Automake::Condition ("C_FALSE"), # From A_TRUE C_FALSE
     new Automake::Condition ("C_TRUE")); # From A_TRUE B_FALSE C_TRUE"

=cut

sub sub_conditions ($$)
{
  my ($self, $subcond) = @_;

  # Make $subcond blindingly apparent in the DisjConditions.
  # For instance '$b->multiply($a->conds)' (from the POD example) is:
  # 	(new Automake::Condition ("FALSE"),
  # 	 new Automake::Condition ("A_TRUE", "B_FALSE", "C_FALSE"),
  # 	 new Automake::Condition ("A_TRUE", "B_FALSE", "C_TRUE"),
  # 	 new Automake::Condition ("FALSE"))
  my @prodconds = $subcond->multiply ($self->conds);

  # Now, strip $subcond from the remaining (i.e., non-false) Conditions.
  my @res = map { $_->false ? () : $_->strip ($subcond) } @prodconds;

  return new Automake::DisjConditions @res;
}

=item C<($string, $ambig_cond) = $condset-E<gt>ambiguous_p ($what, $cond)>

Check for an ambiguous condition.  Return an error message and the
other condition involved if we have an ambiguity.  Return an empty
string and FALSE otherwise.

C<$what> is the name of the thing being defined, to use in the error
message.  C<$cond> is the C<Condition> under which it is being
defined.  C<$condset> is the C<DisjConditions> under which it had
already been defined.

=cut

sub ambiguous_p ($$$)
{
  my ($self, $var, $cond) = @_;

  # Note that these rules don't consider the following
  # example as ambiguous.
  #
  #   if COND1
  #     FOO = foo
  #   endif
  #   if COND2
  #     FOO = bar
  #   endif
  #
  # It's up to the user to not define COND1 and COND2
  # simultaneously.

  return ("$var multiply defined in condition " . $cond->human, $cond)
    if exists $self->{'hash'}{$cond};

  foreach my $vcond ($self->conds)
    {
      return ("$var was already defined in condition " . $vcond->human
	      . ", which includes condition ". $cond->human, $vcond)
	if $vcond->true_when ($cond);

      return ("$var was already defined in condition " . $vcond->human
	      . ", which is included in condition " . $cond->human, $vcond)
	if $cond->true_when ($vcond);
    }
  return ('', FALSE);
}

=head1 SEE ALSO

L<Automake::Condition>.

=head1 HISTORY

C<AM_CONDITIONAL>s and supporting code were added to Automake 1.1o by
Ian Lance Taylor <ian@cygnus.org> in 1997.  Since then it has been
improved by Tom Tromey <tromey@redhat.com>, Richard Boulton
<richard@tartarus.org>, Raja R Harinath <harinath@cs.umn.edu>, Akim
Demaille <akim@epita.fr>, Pavel Roskin <proski@gnu.org>, and
Alexandre Duret-Lutz <adl@gnu.org>.

=cut

1;

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kc3-lang/automake/lib/Automake/DisjConditions.pm

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kc3-lang/automake /lib/Automake/DisjConditions.pm
