StringOrOtherType1

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.

• Download file: File:StringOrOtherType1.txt (change the file extension from txt to pg when you save it)
• File location in NPL: FortLewis/Authoring/Templates/Precalc/StringOrOtherType1.pg

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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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