DotPlusInheritance

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.

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.

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

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