This section of the documentation says # Δ is an alias for Laplacian(), but it is not exported:
(@v1.8) pkg> st ApproxFun
Status `~/.julia/environments/v1.8/Project.toml`
[28f2ccd6] ApproxFun v0.13.0
julia> Δ
ERROR: UndefVarError: Δ not defined
julia> ApproxFun.Δ
ConcreteLaplacian : ApproxFunBase.UnsetSpace() → ApproxFunBase.UnsetSpace()
This section of the documentation says
# Δ is an alias for Laplacian(), but it is not exported:(@v1.8) pkg> st ApproxFun Status `~/.julia/environments/v1.8/Project.toml` [28f2ccd6] ApproxFun v0.13.0 julia> Δ ERROR: UndefVarError: Δ not defined julia> ApproxFun.Δ ConcreteLaplacian : ApproxFunBase.UnsetSpace() → ApproxFunBase.UnsetSpace()