ErrorMessageCustomization

Error Message Customization: PG Code Snippet

This PG code shows how to customize (remap) the error messages students receive after submitting an incorrect response or making a syntax error when entering their answer. This requires using MathObjects or a macro file that loads MathObjects, so that a Context is defined. Note that this is an insertion, not a complete PG file. This code will have to be incorporated into the problem file on which you are working.

Problem Techniques Index

PG problem file	Explanation
loadMacros("PGstandard.pl","MathObjects.pl");	Initialization: To be able to customize the error messages students receive, we must be using MathObjects or a macro that loads MathObjects and has a Context.
Context("Numeric"); Context()->{error}{msg}{"Missing operand after '-'"} = "Enter '-1' instead of '-'"; $ans1 = Real("-1"); $ans2 = Formula("x-2");	Setup: First, specify a Context. One way to remap the error message is through the context. In factoring -x+2 as -(x-2), students may enter - instead of -1 in the first answer box and receive the error message Missing operand after '-'. We can replace this error message with "Enter '-1' instead of '-'" via the Context()->{error}{msg} .... code to the left. The replacement error message can be anything you like as long as it is nonempty. To generate a blank error message, use a quoted space " ", not "". For another way to customize the error message, see the Answer Evaluation section below.
BEGIN_TEXT Factor \( -1 \) from \( -x+2 \). $BR \( -x + 2 = \) \{ ans_rule(5) \} \( \cdot \big( \) \{ ans_rule(10) \} \( \big) \) END_TEXT	Main Text: The problem text section of the file is as we'd expect.
ANS( $ans1->cmp() ); ANS( $ans2->cmp() );	Answer Evaluation: Another way to customize the error message Missing operand after '-' would be to use a post-filter to remove the message after the answer has been graded. The answerHints.pl file provides one way to do this, but it is probably just as easy to do it manually, as in: ANS($eqn->cmp->withPostFilter(sub { my $ans = shift; $ans->{ans_message} = "Enter '-1' instead of '-'" if $ans->{ans_message} eq "Missing operand after '-'"; return $ans; }));

Problem Techniques Index

• POD documentation: answerHints.pl.html
• PG macro: answerHints.pl