3
# - needed since we allow bad pixel handling to be switched off
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use File::Basename qw(&basename &dirname);
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# check for bad value support
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my $bvalflag = $PDL::Config{WITH_BADVAL} || 0;
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# This forces PL files to create target in same directory as PL file.
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# This is so that make depend always knows where to find PL derivatives.
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($file = basename($0)) =~ s/\.PL$//;
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if ($Config{'osname'} eq 'VMS' or
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$Config{'osname'} eq 'OS2'); # "case-forgiving"
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open OUT,">$file" or die "Can't create $file: $!";
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print "Extracting $file (WITH bad value support)\n";
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print "Extracting $file (NO bad value support)\n";
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print OUT <<'!NO!SUBS!';
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# Created by BAD_demo.pm.PL
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# ** DO NOT EDIT THIS FILE **
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package PDL::Demos::BAD_demo;
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PDL::Demos::Routines->import();
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print OUT <<'!NO!SUBS!';
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Your version of PDL has been compiled without support for bad
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values, hence this demo doesn't do anything.
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print OUT <<'!NO!SUBS!';
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Welcome to this tour of the bad value support in PDL
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Each piddle contains a flag - accessible via the badflag() method -
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which indicates whether:
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the piddle contains no bad values (flag equals 0)
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the piddle *MAY* contain bad values (flag equals 1)
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If the flag is set, then the routines (well, those that have been
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converted) will process these bad values correctly, otherwise they
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The code has been written so as to provide as little overhead as
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possible; therefore there should be almost no difference in the
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time it takes to process piddles which do not have their bad flag
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# There are 2 ways to see whether bad-value support has been
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# compiled into your perldl:
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print("You can use bad values.\n") if $PDL::Bad::Status;
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print("You can stil use bad values.\n") if $PDL::Config{WITH_BADVAL};
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# note that PDL::Bad is included by default when you use
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# 'use PDL', 'use PDL::Lite', or 'use PDL::LiteF'
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print( "Bad flag (a) == ", $a->badflag(), "\n" );
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# set bad flag, even though all the data is good
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print( "Bad flag (a) == ", $a->badflag(), "\n" );
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# note the bad flag is infectious
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print( "Bad flag (b) == ", $b->badflag(), "\n\n" );
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# the badflag is also included in the state info of
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$c = pdl(2,3); # just a piddle without the badflag set
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print " Type Dimension State Mem\n";
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print "-------------------------------------------------\n";
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print "a ", $a->info("%-6T %-15D %-5S %12M"), "\n";
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print "b ", $b->info("%-6T %-15D %-5S %12M"), "\n";
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print "c ", $c->info("%-6T %-15D %-5S %12M"), "\n\n";
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print "No bad values: $a\n";
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# set the middle value bad
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print "Some bad values: $a\n";
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print "b contains: $b\n";
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print "so a + b = $c\n\n";
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# The module PDL::Bad contains a number of routines designed
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# to make using bad values easy.
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print "a contains ", $a->nbad, " bad elements.\n";
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print "The bad value for type #",$a->get_datatype," is ",$a->badvalue,"\n";
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print "It is easy to find whether a value is good: ", isgood($a), "\n\n";
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print "or to remove the bad values\n";
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$a->inplace->setbadtoval(23);
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print "a = $a and \$a->badflag == ", $a->badflag, "\n\n";
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print "We can even label certain values as bad!\n";
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$a = $a->setbadif( $a % 2 ); # unfortunately can not be done inplace
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# the issue of how to cope with dataflow is not fully resolved. At
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# present, if you change the badflag of a piddle, all its children
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$a = sequence( byte, 2, 3 );
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$a = $a->setbadif( $a == 3 );
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$b = $a->slice("(1),:");
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print "b = $b\tbadflag = ", $b->badflag, "\n";
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$a->inplace->setbadtoval(3);
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print "b = $b\tbadflag = ", $b->badflag, "\n\n";
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# Note that "boolean" operators return a bad value if either of the
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# operands are bad: one way around this is to replace all bad values
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$a = sequence(3,3); $a = $a->setbadif( $a % 2 );
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print setbadtoval($a > 5,0); # set all bad values to false
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# One area that is likely to cause confusion is the return value from
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# comparison operators (e.g. all and any) when ALL elements are bad.
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# Currently, the bad value is returned; however most code will not
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# be aware of this and just see it as a true or false value (depending
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# on the numerical value used to store bad values).
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# There is also the fact that the bad value need not relate to the
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# type of the input piddle (due to internal conversion to an 'int +').
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$a = ones(3); $a = $a->setbadif( $a == 1 );
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print "Any returns: ", any( $a > 2 ), "\n";
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print "which is the bad value of 'long' (", long->badvalue, ").\n";
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print "Whereas the bad value for \$a is: ", $a->badvalue, "\n";
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Many of the 'core' routines have been converted to handle bad values.
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However, some (including most of the additional modules) have not,
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either because it does not make sense or its too much work to do!
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To find out the status of a particular routine, use the 'badinfo'
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command in perldl (this information is also included when you do
221
'help'), or the '-b' switch of pdldoc.
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print OUT <<'!NO!SUBS!';
added
removed
Demos/BAD_demo.pm.PL
