Hi,
I was wondering if there is a reasonably easy way to format currencies as $1,234,567.00.
In perl, I the Number::Format library, but it is not designated as "safe," and so I cannot use it in the problems that I am drafting.
Is there a workaround for this?
Thank you in advance,
Gabor
You could use the Currency context:
https://github.com/openwebwork/pg/blob/master/macros/contextCurrency.pl
So make:
$c = Currency(1234567);
and $c will display as you asked. You can also customize things with the context flags. Like whether you automatically drop a ".00" at the end. Review the documentation at the top to see all the options.
And here is the POD (plain old documentation) description from the code.
https://demo.webwork.rochester.edu/wwdocs/pg/macros/contextCurrency.pl.html
I don't think anyone has gotten around to writing a tutorial for this in Techniques part of the wiki. (Access to PODs are from the main Author page.)
The short answer is, yes.
A Context is a hash containing information about how MathObjects should be handled. When you create a MathObject (a Formula, a Real, a Currency, etc), that MO itself is a hash that has a reference to a Context (usually the Context that was active at the time the MO was created). For one thing, you can modify that Context mid-problem. Just understand that the MO may be handled differently depending on where in the problem code these things are happening.
Then you can also make new Contexts, changing the active Context. Contexts that were created earlier still exist, and their MathObjects still point to them.
You can have multiple Contexts that are "the same". Meaning, they are different hashes, but have all the same properties.
Example:
Context("Numeric"); # Context "A"
Context()->flags->set(reduceConstants=>0); # modifies Context "A"
$f = Formula("1/2 x^2"); # f is in Context "A"
Context("Numeric"); # Context "B"
$g = Formula("1/2 x^2"); # g is in Context B
$r = $f->eval(x=>2); # $r is a Real in Context "A"
$s = $g->eval(x=>2); # $r is a Real in Context "B"
$r = Real($r); # now $r is a Real in Context "B"
# Printing $f right now in math mode will make `\frac{1}{2} x^2`, because it is in Context "A"
# Printing $g right now in math mode will make `0.5 x^2`, because it is in Context "B"
# Similarly, any context settings that affect answer checking could affect assessing student answers for $f and $g
Yes, there is this:
https://webwork.maa.org/wiki/EquationEvaluators
Some care/awareness is needed to use this. It works by choosing random (x,y) values (or however many variables are in the context) and using a kind of Newton's method to converge toward tuples that solve the equation. And it sees if the same convergence happens for the student answer. There are kinds of equations where that just won't work. See the details in the commentary at:
https://github.com/openwebwork/pg/blob/master/macros/parserImplicitEquation.pl
Hi Gabor,
Since WeBWorK does not have a CAS, it doesn't have what I think you are describing.
You can have a WeBWorK problem appeal to Sage for certain things. Try leveraging what is here:
https://webwork.maa.org/wiki/AskSage
It has been a long time since I tried to use this. IIRC, occasionally you will have to be careful with the syntax that PG understands versus the syntax that Sage understands. And it sounds like you may be interested in using AskSage within a custom answer checker, not just using it to produce something to present in the exercise statement.
Alex