## WeBWorK Problems

### Making A Currency object with a PiecewiseFunction object

by Robin Cruz -
Number of replies: 2

I am trying to use a Piecewise function to calculate values and then convert these values to Currency objects-- so far, I'm not getting it to work.  When the answer is submitted it is scored as incorrect and the message is displayed: "Unexpected charactoer '$' " The code I've gotten so far is listed below. Thanks -- rac ----------------------------------------------------------------------------------- DOCUMENT(); # This should be the first executable line in the problem. loadMacros( "PGstandard.pl", "MathObjects.pl", "contextCurrency.pl", "contextPiecewiseFunction.pl" ); TEXT(&beginproblem); ###################################### # Setup Context("PiecewiseFunction");$x1 = random(5000,7000,1000);
$x2 = random(8000,12000,1000);$m1 = random(.02,.04,.01);
$m2 =$m1 + random(.02,.04,.01);
$b2 =$m1*$x1;$m3 = $m2 + random(.01,.02,.01);$b3 = $b2+$m2*($x2-$x1);

$T = Formula("$m1 x if x <= $x1 else$b2 + $m2 (x -$x1) if $x1 < x <=$x2
else $b3 +$m3 (x -$x2) if x >$x2");

Context("Numeric");

$input = random(4000,15000,10);$tax = $T->eval(x=>$input)->inContext(Context());

Context("Currency");

$income = Currency($input);

#####################################
#  Main text

BEGIN_TEXT
Suppose the state income tax for a single person in 2005 was
determined by the rule
$T(x) = \{T->TeX\}$
where $$x$$ is the taxable income for a single person.  Find the tax due on the income:
$PAR For$income the tax = \{ans_rule(15)\}

END_TEXT

######################################

ANS(Currency($tax)->cmp); ###################################### ENDDOCUMENT(); In reply to Robin Cruz ### Re: Making A Currency object with a PiecewiseFunction object by Davide Cervone - You are doing some very sophisticated coding. Nice work. The program is actually correct; it turns out that there was a but in the Currency context that would allow Currency($tax) to return a Real rather than a Currency object, and that's why the $was not defined for this answer. I have fixed the macros/contextCurrency.pl file (and also lib/Value/Real.pm and lib/Value/Complex/pm) to correct this error. You will need to update those files to get your problem to work correctly. One small optimization I might recommend for you. I think that  Context("Numeric");$input = random(4000,15000,10);
$tax =$T->eval(x=>$input)->inContext(Context()); Context("Currency");$income = Currency($input); . . . ANS(Currency($tax)->cmp);

could be replaced by
    Context("Currency");
$input = random(4000,15000,10);$tax = Currency($T->eval(x=>$input));
$income = Currency($input);
.
.
.
ANS(\$tax->cmp);

There is no need to go to the Numeric context, and using Currency() at this point makes it unnecessary to do the inContext() call.

Hope that helps.

Davide