View of /trunk/pg/macros/answerVariableList.pl

    1 loadMacros('Parser.pl');
    2 
    3 sub _answerVariableList_init {}; # don't reload this file
    4 
    5 =head1 DESCRIPTION
    6 
    7 ######################################################################
    8 #
    9 #  This answer checker compares the student answer to a list of
   10 #  variable names (so, for example, you can ask for what values a
   11 #  given function depends on).
   12 #
   13 #  Use addVariables() to create the list of variables that from which
   14 #  the student can choose, and then use variable_cmp() to generate the
   15 #  answer checker.  If the formula passed to variable_cmp contains
   16 #  parentheses around the list, then the student's answer must as
   17 #  well.
   18 #
   19 #  You can also include additional parameters to variable_cmp.  These
   20 #  can be any of the flags appropriate for List() answer checker.
   21 #
   22 #  Usage examples:
   23 #
   24 # addVariables('x','y','z');
   25 # ANS(variable_cmp("(x,y)"));
   26 #
   27 # addVariables('x','y','z','s','t,);
   28 # ANS(variable_cmp("s,t"));
   29 #
   30 # addVariables('x','y','z');
   31 # ANS(variable_cmp("(x)",showHints=>0,showLengthHints=>0));
   32 #
   33 
   34 #
   35 #  A new context for variable lists
   36 #
   37 
   38 =cut
   39 
   40 
   41 $context{VariableList} = Parser::Context->new(
   42   operators => {',' => Context()->operators->get(',')},
   43   lists => {'List'  => {class =>'Parser::List::List'}},
   44   parens => {
   45    '(' => {close => ')', type => 'List', formList => 1},
   46    'start' => {close => 'start', type => 'List', formList => 1,
   47                removable => 1, emptyOK => 1, hidden => 1},
   48    'list'  => {type => 'List', hidden => 1},
   49   },
   50   flags => {
   51     NumberCheck =>
   52       sub {shift->Error("Entries in your list must be variable names")},
   53     formatStudentAnswer => 'evaluated',  # or 'parsed' or 'reduced'
   54   },
   55 );
   56 Context("VariableList");
   57 
   58 #
   59 #  A shell that calls Formula()->cmp with the right defaults
   60 #
   61 sub variable_cmp {
   62   Value::Formula->new(shift)->cmp(
   63     ordered => 1,
   64     entry_type =>'a variable',
   65     list_type => 'a list',
   66     implicitList => 0,
   67     @_
   68   );
   69 }
   70 
   71 #
   72 #  Handy routine to set up variables
   73 #
   74 sub addVariables {
   75   my $context = Context();
   76   foreach my $v (@_) {$context->variables->add($v=>'Real')}
   77 }
   78 
   79 1;