Package to work with piecewise functions?

General Usage
3

Thanks for your reply! In our use case, we would like to use Symbolics.jl to take derivatives rather than ForwardDiff.jl. In particular, the issue I keep running into is the following issue:

julia> f(x) = x ≤ 0 ? exp(x) : x+1
f (generic function with 1 method)

julia> using Symbolics

julia> @syms x
(x,)

julia> f(x)
ERROR: MethodError: no method matching isless(::SymbolicUtils.BasicSymbolic{Number}, ::Int64)
Closest candidates are:
  isless(::Union{StatsBase.PValue, StatsBase.TestStat}, ::Real) at ~/.julia/packages/StatsBase/XgjIN/src/statmodels.jl:90
  isless(::ColorTypes.AbstractGray, ::Real) at ~/.julia/packages/ColorTypes/1dGw6/src/operations.jl:38
  isless(::SymbolicUtils.Symbolic{<:Real}, ::Real) at ~/.julia/packages/SymbolicUtils/Vzo2s/src/methods.jl:173
  ...
Stacktrace:
 [1] <(x::SymbolicUtils.BasicSymbolic{Number}, y::Int64)
   @ Base ./operators.jl:356
 [2] <=(x::SymbolicUtils.BasicSymbolic{Number}, y::Int64)
   @ Base ./operators.jl:405
 [3] f(x::SymbolicUtils.BasicSymbolic{Number})
   @ Main ./REPL[9]:1
 [4] top-level scope
   @ REPL[12]:1

julia>

Edit: After having a look at this thread, the following MWE seems pretty good for my needs

julia> f(x) = ifelse(x ≤ 0.0, exp(2*x), x^2+1)
f (generic function with 1 method)

julia> using Symbolics

julia> @syms x::Real
(x,)

julia> f(x)
ifelse(x <= 0.0, exp(2x), 1 + x^2)

julia> Symbolics.derivative(f(x), x)
ifelse(x <= 0.0, 2exp(2x), 2x)

Eventually, I also want to support multiple intervals, so I came up with the (admittedly clunky) solution for the case of two intervals

julia> ifelse2(c1, c2, x, y, z) = ifelse(c1, x, ifelse(!c2, y, z))
ifelse2 (generic function with 1 method)

julia> f2(x) = ifelse2(x ≤ 2, x > 4, x^2, exp(2*x), 4*x)
f2 (generic function with 1 method)

julia> Symbolics.derivative(f2(x), x)
ifelse(x <= 2, 2x, ifelse(!(x > 4), 2exp(2x), 4))