Teacher Language
Flexible language for defining grades calculations.
How to use
Let's say you have some really complex calculations to do for every student:
there's three exams (e1, e2 and e3), a homework (hw) and a replacement exam
(re) that replaces the lowest score. The final grade (fg) is given by the
following calculation: fg=(3*(2*e1+2*e2+3*e3)/7+hw)/4.
Example:
| e1 | e2 | e3 | re | hw | fg |
|---|---|---|---|---|---|
| 8.0 | 6.0 | 4.0 | 6.0 | 6.0 | 6.43 |
How could you describe this problem in a clear, flexible way? Would you simply hard-code this particular solution? What if any user of your system could create their own arbitrary solution?
Consider the following code:
# Assign values to variables
e1=8
e2=6
e3=4
hw=6
re=6
# Publish these variables
pub(e1)
pub(e2)
pub(e3)
pub(hw)
pub(re)
# Returns the smaller expression *in a symbolic way*
smaller=min(e1,e2,e3)
# Substitute the *variable* on the left by the right one
# *ONLY* expressions that return identifiers should be
# used on the left side
sub(smaller,re)
# Calculate the final grade
fg=(3*(2*e1+2*e2+3*e3)/7+hw)/4
pub(fg)
Interpreting the language:
require 'teacher'
require 'csv'
teacher = Teacher::Base.new
teacher.run(File.read("example.teacher"))
scope = teacher.scope
CSV.generate do |csv|
csv << scope.published_variables.keys
csv << scope.published_variables.values
end
# => e1, e2, e3, hw, re, fg
# 8.0,6.0,4.0,6.0,6.0,6.428571428571429
scope.published_variables # => {"e1"=>8.0,
# "e2"=>6.0,
# "e3"=>4.0,
# "hw"=>6.0,
# "re"=>6.0,
# "fg"=>6.428571428571429}
scope.symbols # => { ...
# "e1"=>8.0,
# "e2"=>6.0,
# "e3"=>6.0,
# "hw"=>6.0,
# "re"=>6.0,
# "smaller"=> Identifier (e3 = 4.0),
# "fg"=>6.428571428571429}