Minor cleanup

[HarrisonGrodin]

Closes #99, closes #100, closes #101.

[HarrisonGrodin]

It seems like we should try to be consistent with how we shorten macro names. Some ideas:

# Option A
@param t σ
@var x(t) y(t)
@deriv D'~t

# Option B
@parameter t σ
@variable x(t) y(t)
@derivative D'~t D''~t

We could also pluralize. Thoughts? @ChrisRackauckas @dpsanders

[codecov]

Codecov Report

Merging #103 into master will increase coverage by 1.26%.
The diff coverage is 82.85%.

@@            Coverage Diff             @@
##           master     #103      +/-   ##
==========================================
+ Coverage   92.02%   93.29%   +1.26%     
==========================================
  Files          11       11              
  Lines         326      328       +2     
==========================================
+ Hits          300      306       +6     
+ Misses         26       22       -4

Impacted Files	Coverage Δ
src/ModelingToolkit.jl	75% <ø> (ø)	⬆️
src/utils.jl	87.5% <ø> (ø)	⬆️
src/function_registration.jl	100% <100%> (ø)	⬆️
src/systems/diffeqs/first_order_transform.jl	100% <100%> (ø)	⬆️
src/systems/diffeqs/diffeqsystem.jl	94.23% <100%> (ø)	⬆️
src/simplify.jl	95% <100%> (ø)	⬆️
src/differentials.jl	97.72% <100%> (ø)	⬆️
src/equations.jl	92% <50%> (ø)	⬆️
src/variables.jl	86.48% <66.66%> (+1.87%)	⬆️
src/operations.jl	92.85% <83.33%> (+21.42%)	⬆️

---

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[ChrisRackauckas]

I think Option A is fine, but I think @dpsanders likes the full names?

[HarrisonGrodin]

Whoa, this has a version-based bug - works on 1.1/nightly, but not on 1.0.

[HarrisonGrodin]

The more I look at the options, I like the full names (Option B) - since these lines will only be typed a few times at the beginning of each model, it seems reasonable to make the names slightly more verbose/clear. I also think pluralizing will help with this goal.

@parameters t σ
@variables x(t) y(t)
@derivatives D'~t D''~t

@ChrisRackauckas Am I good to change this?

[ChrisRackauckas]

Yeah that looks good.

[HarrisonGrodin]

Update: the reason 1.1 works (while 1.0 fails) seems to be due to JuliaLang/julia#29668. This does beg the question of whether or not we should have comparison functions return non-booleans (outside of an explicit context), though.

[ChrisRackauckas]

What booleans would they return?