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

    1 =head1 NAME
    2 
    3 answerVariableList.pl - Creates answer checkers that compare the student's
    4 answer to a list of variable names.
    5 
    6 =cut
    7 
    8 loadMacros('MathObjects.pl');
    9 
   10 sub _answerVariableList_init {
   11   #
   12   #  A new context for variable lists
   13   #
   14   $main::context{VariableList} = Parser::Context->new(
   15     operators => {',' => $Parser::Context::Default::context{Full}->operators->get(',')},
   16     lists => {'List'  => {class =>'Parser::List::List'}},
   17     parens => {
   18      '(' => {close => ')', type => 'List', formList => 1},
   19      'start' => {close => 'start', type => 'List', formList => 1,
   20                  removable => 1, emptyOK => 1, hidden => 1},
   21      'list'  => {type => 'List', hidden => 1},
   22     },
   23     flags => {
   24       NumberCheck =>
   25         sub {shift->Error("Entries in your list must be variable names")},
   26       formatStudentAnswer => 'evaluated',  # or 'parsed' or 'reduced'
   27     },
   28   );
   29 
   30   main::Context("VariableList");  ### FIXME:  probably should require author to set this explicitly.
   31 }
   32 
   33 =head1 MACROS
   34 
   35 =head2 variable_cmp
   36 
   37  ANS(variable_cmp($var_string, %options))
   38 
   39 This answer checker compares the student answer to a list of
   40 variable names (so, for example, you can ask for what values a
   41 given function depends on).
   42 
   43 Use addVariables() to create the list of variables that from which
   44 the student can choose, and then use variable_cmp() to generate the
   45 answer checker.  If the formula passed to variable_cmp contains
   46 parentheses around the list, then the student's answer must as
   47 well.
   48 
   49 You can also include additional parameters to variable_cmp.  These
   50 can be any of the flags appropriate for List() answer checker.
   51 
   52 Usage examples:
   53 
   54     addVariables('x','y','z');
   55     ANS(variable_cmp("(x,y)"));
   56 
   57     addVariables('x','y','z','s','t,);
   58     ANS(variable_cmp("s,t"));
   59 
   60     addVariables('x','y','z');
   61     ANS(variable_cmp("(x)",showHints=>0,showLengthHints=>0));
   62 
   63 =cut
   64 
   65 sub variable_cmp {
   66   Value->Package("Formula")->new(shift)->cmp(
   67     ordered => 1,
   68     entry_type =>'a variable',
   69     list_type => 'a list',
   70     implicitList => 0,
   71     @_
   72   );
   73 }
   74 
   75 =head2 addVariables
   76 
   77  addVariables(@vars)
   78 
   79 Adds each string in @vars as a varible to the current context.
   80 
   81 =cut
   82 
   83 sub addVariables {
   84   my $context = Context();
   85   foreach my $v (@_) {$context->variables->add($v=>'Real')}
   86 }
   87 
   88 1;
   89