DotPlusInheritance.jl

Expression parser that simulates type inheritance
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Updated Last
4 Years Ago
Started In
January 2015

DotPlusInheritance

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What is this?

Not really a solution for inheritance, but a simple way for evaluating expressions when u think having inheritance relationships between involved types could simplifies expressions and help modeler do better.

How, when, and for whom it helps?

Julia dose not supports inheritance like standard object oriented langs e.g.(c++ or java). But inheritance really is a good feature when creating mathematical models of real world objects. I solve this problem for myself (when modeling process equipments) by writing a this simple module that simulates Type Inheritance. This trick creates a direct way to address all variables of member variables with special prefix before their names (at this time prefix is __base__) by using their Symbols. Although it's not really inheritance, now i can define a Special Pump type that have all variables of a Basic one. and evaluate expressions like: :(mypump.anSpecialPump_variable*mypump.aBasicPump_variable) in place of
:(mypump.anSpecialPump_mv*mypump.basicPumpModel.aBasicPump_mv) this really simplifies creating large models of various equipment each with many equations.

Defines:

dotplus(t::DataType,ex::Union(Expr,Symbol)) 
dotplus(var::Symbol,ex::Union(Expr,Symbol)) 
(.+)(var::Symbol,ex::Union(Expr,Symbol))

Usage:

1- install, download package files and copy DotPlusInheritance.jl folder to your Pkg.dir()

2- use DotPlusInheritance

3- in child type use base as a member with _base_ prefix

type BaseModel
  a
  b
end
type ChildModel
  _base_1::BaseModel
  a
  c
end

4- generate a dot expression to address a base member from child type

@test dotplus(ChildModel,:b) == :(_base_1.b)

5- use dotplus(::Symbol,::Union(Expr,Symbol)) to address a base member from a drived variable

6- or use .+ to get value

m1=BaseModel(1,2)
@test dotplus(:m1,:a) == :(m1.a)
@test :m1.+:a == m1.a
m2=ChildModel(m1,3,4)
#Over write
@test dotplus(:m2,:a) == :(m2.a)
@test :m2.+:a == m2.a
#Base member 
@test dotplus(:m2,:b) == :(m2._base_1.b)
@test :m2.+:b == m2._base_1.b
@test dotplus(:m2,:c) == :(m2.c)
@test :m2.+:c == m2.c