My name is Lee McPherson and I'm a part-time chemistry instructor at Portland Community College. I've been working on software for both chemistry and general amusement for several different platforms for a little while. However, I had always been interested in making software that can understand significant figures and do math operations with them. It started in C# but I have since discovered the WeBWorK platform and decided to use it instead. All of this work is at the following github repo: limefrogyank/WeBWorKChemistry: WeBWorK scripts for doing problems related to Chemistry (and beyond!) (github.com)
I'm posting this now, because I would seriously love some help expanding this content and testing it. We're slowly building some course content using these tools and discovering flaws to fix, but hope to have it up and running by winter term.
You can create an InexactValue with a string:
You can create one with a number and explicit number of sig figs:
InexactValue(2, 3); # essentially creates the value 2.00
You can even explicitly make the value exact. (This is useful when you want to use the methods on InexactValue. It will also be useful later with units.)
The methods include getting the number of sig figs. This is useful for questions asking a student how many significant figures a number might have:
Best of all, you can do math with InexactValue and the correct significant figures are calculated according to the standard rules taught in most chemistry courses.
$result = InexactValue("4.00") * InexactValue("2.0");
# $result contains an InexactValue with value of 8 and 2 significant figures. The string output will be "8.0".
This is an extension of InexactValue with a modified version of the units macro. To make an InexactValueWithUnits, you provide exactly what you would provide a normal InexactValue as an array for the first parameter, then the units for the second parameter.
$n1 = InexactValueWithUnits('1.609', 'km');
$d1 = InexactValueWithUnits(['1', Infinity], 'mi');
When you do math with these values, the units automatically combine correctly:
$result = $n1/$d1;
# using values above
# $result contains an InexactValueWithUnits that will output the string: 1.609 km mi^-1
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