Reduce allocations to improve speed

- Return tuples instead of 1x2 arrays in internal functions
- Return a tuple instead of a 1x2 array for public-facing functions
  when called with a single point
- Add tests for the equivalence of calling the single-point methods
  multiple times, and calling the multiple-point methods once
- Bump minor version number since the API is changed for the
  single-point methods (these now return tuples):
  - convert_bng(lon, lat)
  - convert_lonlat(E, N)

These changes appear to offer a 15-20% increase in speed.

Author: anowacki

Project.toml

@@ -1,7 +1,7 @@
 name = "ConvertBNG"
 uuid = "76c420ca-8e5d-4181-817d-b9cafca33221"
 authors = ["Joshua Nunn <joshuanunn@hotmail.co.uk>"]
-version = "0.3.1"
+version = "0.4.0"
 
 [deps]
 DelimitedFiles = "8bb1440f-4735-579b-a4ab-409b98df4dab"

src/ConvertBNG.jl

@@ -135,7 +135,7 @@ Perform Longitude, Latitude to ETRS89 conversion
     north = I + II * l ^ 2 + III * l ^ 4 + IIIA * l ^ 6
     east = E₀ + IV * l + V * l ^ 3 + VI * l ^ 5
 
-    return [east north]
+    return east, north
 end
 
 """
@@ -184,7 +184,7 @@ Note that either GRS80 or Airy 1830 ellipsoids can be passed
     ϕ = rad2deg(ϕ)
     λ = rad2deg(λ)
     λ, ϕ = round_to_eight(λ, ϕ)
-    return [λ ϕ]
+    return λ, ϕ
 end
 
 function convert_etrs89_to_ll(E::T, N::T) where {T<:Real}
@@ -207,7 +207,7 @@ function convert_osgb36(lonlat::Array{T,2}) where{T<:Real}
     en_arr = zeros(T, size(lonlat))
     # Transform
     Threads.@threads for i in 1:size(lonlat)[1]
-        en_arr[i,:] = convert_osgb36(lonlat[i,1], lonlat[i,2])
+        en_arr[i,:] .= convert_osgb36(lonlat[i,1], lonlat[i,2])
     end
     return en_arr
 end
@@ -220,7 +220,7 @@ function convert_osgb36_nothread(lonlat::Array{T,2}) where{T<:Real}
     en_arr = zeros(T, size(lonlat))
     # Transform
     for i in 1:size(lonlat)[1]
-        en_arr[i,:] = convert_osgb36(lonlat[i,1], lonlat[i,2])
+        en_arr[i,:] .= convert_osgb36(lonlat[i,1], lonlat[i,2])
     end
     return en_arr
 end
@@ -232,7 +232,7 @@ function convert_etrs89_to_osgb36(E::T, N::T) where {T<:Real}
     # Obtain OSTN15 corrections, and incorporate
     e_shift, n_shift, _ = ostn15_shifts(E, N)
     e_corr, n_corr = round_to_mm(E + e_shift, N + n_shift)
-    return [e_corr n_corr]
+    return e_corr, n_corr
 end
 
 """
@@ -250,7 +250,7 @@ function convert_osgb36_to_ll(en::Array{T,2}) where{T<:Real}
     ll_arr = zeros(T, size(en))
     # Transform
     Threads.@threads for i in 1:size(en)[1]
-        ll_arr[i,:] = convert_osgb36_to_ll(en[i,1], en[i,2])
+        ll_arr[i,:] .= convert_osgb36_to_ll(en[i,1], en[i,2])
     end
     return ll_arr
 end
@@ -263,7 +263,7 @@ function convert_osgb36_to_ll_nothread(en::Array{T,2}) where{T<:Real}
     ll_arr = zeros(T, size(en))
     # Transform
     for i in 1:size(en)[1]
-        ll_arr[i,:] = convert_osgb36_to_ll(en[i,1], en[i,2])
+        ll_arr[i,:] .= convert_osgb36_to_ll(en[i,1], en[i,2])
     end
     return ll_arr
 end
@@ -289,7 +289,7 @@ function convert_osgb36_to_etrs89(E::T, N::T) where {T<:Real}
     end
     x = E - dx
     y = N - dy
-    return [x y]
+    return x, y
 end
 
 """