More informative errors for finite mps (#367)

* specify method

* check spacetype

* be happy with anything that acts like a vector

Author: borisdevos

src/algorithms/toolbox.jl

@@ -94,7 +94,7 @@ function transfer_spectrum(
     init = randomize!(
         similar(
             above.AL[1], left_virtualspace(below, 1),
-            ℂ[typeof(sector)](sector => 1)' * left_virtualspace(above, 1)
+            spacetype(above)(sector => 1)' * left_virtualspace(above, 1)
         )
     )
 
@@ -151,7 +151,7 @@ function marek_gap(above::InfiniteMPS; tol_angle = 0.1, kwargs...)
     return marek_gap(spectrum; tol_angle)
 end
 
-function marek_gap(spectrum; tol_angle = 0.1)
+function marek_gap(spectrum::AbstractVector{T}; tol_angle = 0.1) where {T <: Number}
     # Remove 1s from the spectrum
     inds = findall(abs.(spectrum) .< 1 - 1.0e-12)
     length(spectrum) - length(inds) < 2 || @warn "Non-injective mps?"
@@ -187,7 +187,7 @@ function correlation_length(above::InfiniteMPS; kwargs...)
     return 1 / ϵ
 end
 
-function correlation_length(spectrum; kwargs...)
+function correlation_length(spectrum::AbstractVector{T}; kwargs...) where {T <: Number}
     ϵ, = marek_gap(spectrum; kwargs...)
     return 1 / ϵ
 end