StringOrOtherType1

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Answer is a String, or a Number, or a Function, etc.

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This PG code shows how to prevent error messages from appearing when an answer may be one of several data types.


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PG problem file Explanation

Problem tagging data

Problem tagging:

DOCUMENT();

loadMacros(
"PGstandard.pl",
"MathObjects.pl",
"AnswerFormatHelp.pl",
);

TEXT(beginproblem());

Initialization:

Context("Numeric");

$y = random(0,4,1);

if ($y < 4) {
   $answer = String("none");
} else {
   $answer = Formula("2*x");
}

Setup: There are several predefined strings, such as NONE, DNE, INF, INFINITY. If you need another string added to the context, see strings in context.

Context()->texStrings;
BEGIN_TEXT
Is there a line through the points \( (0,0) \), 
\( (1,2) \), and \( (2,$y) \)?  If there is, 
the equation for this line.  If not, enter
${BITALIC}NONE${EITALIC}.
$BR
$BR
\( y = \) \{ ans_rule(20) \}
\{ AnswerFormatHelp("formulas") \}
END_TEXT
Context()->normalStrings;

Main Text:

$showPartialCorrectAnswers = 1;

ANS( $answer->cmp( typeMatch=>Formula("x") ) );

Answer Evaluation: When $answer = Formula("2*x") and a student enters the string NONE, they will not get any error message because when the answer checker expects a formula and gets a string it is set up not to balk. However, when $answer = String("none") and a student enters the formula 2x, they will get an error message. This is because the answer checker is expecting a string and gets a formula, and when this happens it balks. We must use typeMatch=>Formula("x") so that in the event the answer is a string, no error message will appear.

Context()->texStrings;
BEGIN_SOLUTION
${PAR}SOLUTION:${PAR}
Solution explanation goes here.
END_SOLUTION
Context()->normalStrings;

COMMENT('MathObject version.');

ENDDOCUMENT();

Solution:

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