# Extending Symbolics.jl, How to dispatch all functions to the underlying Num
**URL:** https://discourse.julialang.org/t/extending-symbolics-jl-how-to-dispatch-all-functions-to-the-underlying-num/106845
**Category:** Modelling & Simulations
**Tags:** question, package, sciml, symbolics
**Created:** [November 28, 2023, 12:29pm UTC](https://discourse.julialang.org/t/extending-symbolics-jl-how-to-dispatch-all-functions-to-the-underlying-num/106845 "2023-11-28T12:29:23Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@Qfl3x](https://discourse.julialang.org/u/Qfl3x)
#### Post date: [November 28, 2023, 12:29pm UTC](https://discourse.julialang.org/t/extending-symbolics-jl-how-to-dispatch-all-functions-to-the-underlying-num/106845/1 "2023-11-28T12:29:23Z")
Hello, I want to extend Symbolics.jl Variables to encode bounds and default value of parameters in the “variable”; Currently something like this:
```julia
using Symbolics: _parse_vars, Num, @variables
import SciMLBase: issymbollike
import Base: +, -, *, /
struct Parameter
var::Num
lower::Real
upper::Real
default::Real
end
# Extended Functions:
Base.:+(p::Parameter, x::Any) = Base.:+(p.var, x)
Base.:-(p::Parameter, x::Any) = Base.:-(p.var, x)
Base.:/(p::Parameter, x::Any) = Base.:/(p.var, x)
Base.:*(p::Parameter, x::Any) = Base.:*(p.var, x)
issymbollike(::Parameter) = true
macro parameter(x, lower, upper, default)
var = (@variables $x)[1]
esc(Parameter(var, lower, upper, default))
end
function bounds(p::Parameter)
return (p.lower, p.upper)
end
```
I want all functions (except a few pre-determined ones like `bounds`) to act directly on `p.var` without having to extend everything by hand like the `Base.:` block.
---
### Author:  [@SteffenPL](https://discourse.julialang.org/u/SteffenPL)
#### Post date: [November 28, 2023, 12:34pm UTC](https://discourse.julialang.org/t/extending-symbolics-jl-how-to-dispatch-all-functions-to-the-underlying-num/106845/2 "2023-11-28T12:34:17Z")
Maybe you could get some inspiration from here which already implemented bounds [Symbolic Metadata · ModelingToolkit.jl (sciml.ai)](https://docs.sciml.ai/ModelingToolkit/stable/basics/Variable_metadata/).
---
### Author:  [@Qfl3x](https://discourse.julialang.org/u/Qfl3x)
#### Post date: [November 28, 2023, 1:34pm UTC](https://discourse.julialang.org/t/extending-symbolics-jl-how-to-dispatch-all-functions-to-the-underlying-num/106845/3 "2023-11-28T13:34:13Z")
That should do!
Though I may need “mandatory” metadata for my case, will see how it goes.