Example

## Set up a matched list by creating a new matched list object.
## $matched_list_ptr points to a new matched list object.
$matched_list_ptr = new_match_list();
  
## Now assign to the matched list object an array of "question", "answer" 
## pairs from which a subset will be selected.
##
$matched_list_ptr -> qa ("R stands for", "Red",
                         "O stands for", "Orange", 
                         "Y stands for", "Yellow", 
                         "G stands for", "Green", 
                         "B stands for", "Blue", 
                         "I stands for", "Indigo",
                         "V stands for", "Violet"
                         );

## Choose four of the possible question-answer pairs
$matched_list_ptr -> choose(4);

## Ok, we are ready to begin...
##

TEXT(beginproblem());


## In the text block below, we will print the 
## selection questions with (uncommented of course)
## \{ $matched_list_ptr -> print_q \}

## and corresponding (and permuted) answers with
## Print the corresponding answers
## \{ $matched_list_ptr -> print_a \}

BEGIN_TEXT
$PAR
This problem below is a matching problem
using four of seven possible questions and corresponding answers.  
$BR

$BBOLD Matching Problem 1: $EBOLD In the colors of the visible light
spectrum, the acronym ROYGBIV is often used.  $BR 

Here is the list of questions:
\{ $matched_list_ptr -> print_q \}
$PAR

Here is the (permuted list) of answers
\{ $matched_list_ptr -> print_a \}

END_TEXT

## Provide the answer string
ANS( str_cmp( $matched_list_ptr->ra_correct_ans ) ) ;
              
## Now a simple matching example using questions in math mode
## Note the invocation of math mode is inside the (double) quotes
## which define the question-answer pairs
##
$new_matched_list_ptr = new_match_list();

$new_matched_list_ptr -> qa ("\( \tan^{-1}x \)",
                             "\( \displaystyle{\frac{1}{1+x^2}} \)",
                             "\( \ln(1 + x^2) \)",
                             "\( \displaystyle{\frac{2x}{1+x^2}} \)",
                             "\( \ln(\sqrt{1+x^2}) \)",
                             "\( \displaystyle{\frac{x}{1+x^2}} \)"
                             );
## Choose all three of the possible question-answer pairs
$new_matched_list_ptr -> choose(3);

BEGIN_TEXT
$PAR
This problem below is a matching problem
using all three possible questions and corresponding answers.  
$BR

$BBOLD Matching Problem 2: $EBOLD Match the functions to their derivatives
$BR 

Here is the list of questions:
\{ $new_matched_list_ptr -> print_q \}
$PAR

Here is the (permuted list) of answers
\{ $new_matched_list_ptr -> print_a \}

END_TEXT

## Provide the answer string
ANS( str_cmp( $new_matched_list_ptr->ra_correct_ans ) ) ;