I would like to hear the opinions of @odow @trulsf for JuMP and maybe @ChrisRackauckas or @YingboMa for ModelingToolkit.jl.
What would you prefer the behavior to be when you try to add two quantities that have incompatible SymbolicDimensions?
First, recall that SymbolicDimensions is a way to avoid automatically converting to SI base units:
For example:
```julia
julia> q = 4us"kPa * Constants.c"
4.0 kPa c
julia> sqrt(q)
2.0 kPa¹ᐟ² c¹ᐟ²
```
Only when you call `expand_units` would it convert from `SymbolicDimensions` to `Dimensions`:
```julia
julia> expand_units(q)
1.199169832e12 kg s⁻³
```
Right now when you try to add two incompatible quantities, the behavior is:
julia> 1us"km/s" + 1us"m/s"
ERROR: DimensionError: 1.0 s⁻¹ km and 1.0 m s⁻¹ have incompatible dimensions
whereas with regular Dimensions, you get:
julia> 1u"km/s" + 1u"m/s"
1001.0 m s⁻¹
Questions for you: is this behavior good as-is? Or should there be some way to automatically convert to SI units when this happens, but stay in SymbolicDimensions (to avoid type instability)?
Another option would be to perform all computations with Dimensions, and then display by converting back to SymbolicDimensions. For example:
julia> output_units = us"km/hr";
julia> a = 15us"km/hr"; b = 30us"m/s";
julia> raw_output = expand_units(a) + expand_units(b)
34.166666666666664 m s⁻¹
julia> as_units(q, units) = Quantity(ustrip(q / expand_units(units)) * ustrip(units), dimension(units));
julia> as_units(raw_output, output_units)
122.99999999999999 km hr⁻¹
I would like to hear the opinions of @odow @trulsf for JuMP and maybe @ChrisRackauckas or @YingboMa for ModelingToolkit.jl.
What would you prefer the behavior to be when you try to add two quantities that have incompatible
SymbolicDimensions?First, recall that SymbolicDimensions is a way to avoid automatically converting to SI base units:
For example: ```julia julia> q = 4us"kPa * Constants.c" 4.0 kPa c julia> sqrt(q) 2.0 kPa¹ᐟ² c¹ᐟ² ``` Only when you call `expand_units` would it convert from `SymbolicDimensions` to `Dimensions`: ```julia julia> expand_units(q) 1.199169832e12 kg s⁻³ ```Right now when you try to add two incompatible quantities, the behavior is:
whereas with regular
Dimensions, you get:Questions for you: is this behavior good as-is? Or should there be some way to automatically convert to SI units when this happens, but stay in
SymbolicDimensions(to avoid type instability)?Another option would be to perform all computations with
Dimensions, and then display by converting back toSymbolicDimensions. For example: