Fail gracefully if file NP.xy is missing

README.md

@@ -38,6 +38,15 @@ julia> Pkg.add("AstroLib")
 You may need to update your package list with `Pkg.update()` in order to get the
 latest version of `AstroLib.jl`.
 
+Note that, in order to work, a few functions require external files, which are
+automatically downloaded when building the package.  Should these files be
+missing for some reason, you will be able to load the package but some functions
+may not work properly.  You can manually build the package with
+
+```julia
+julia> Pkg.build("AstroLib")
+```
+
 Usage
 -----
 

docs/index.rst

@@ -30,19 +30,28 @@ be installed with `Julia built-in package
 manager <http://docs.julialang.org/en/stable/manual/packages/>`__. In a
 Julia session run the command
 
-.. code:: julia
+.. code-block:: julia
 
     julia> Pkg.add("AstroLib")
 
 You may need to update your package list with ``Pkg.update()`` in order
 to get the latest version of ``AstroLib.jl``.
 
+Note that, in order to work, a few functions require external files, which are
+automatically downloaded when building the package.  Should these files be
+missing for some reason, you will be able to load the package but some functions
+may not work properly.  You can manually build the package with
+
+.. code-block:: julia
+
+    julia> Pkg.build("AstroLib")
+
 Usage
 -----
 
 After installing the package, you can start using ``AstroLib.jl`` with
 
-.. code:: julia
+.. code-block:: julia
 
     using AstroLib
 
@@ -66,7 +75,7 @@ fields are
 The type constructor ``Observatory`` can be used to create a new
 ``Observatory`` object. Its syntax is
 
-.. code:: julia
+.. code-block:: julia
 
     Observatory(name, lat, long, alt, tz)
 
@@ -79,7 +88,7 @@ A predefined list of some observing sites is provided with
 abbreviated names of the observatories. For example, you can access information
 of the European Southern Observatory with
 
-.. code:: julia
+.. code-block:: julia
 
     julia> obs = AstroLib.observatories["eso"]
     Observatory: European Southern Observatory
@@ -93,7 +102,7 @@ of the European Southern Observatory with
 
 You can list all keys of the dictionary with
 
-.. code:: julia
+.. code-block:: julia
 
     keys(AstroLib.observatories)
 
@@ -125,15 +134,15 @@ System planets. Its fields are
 
 The constructor has this syntax:
 
-.. code:: julia
+.. code-block:: julia
 
     Planet(name, radius, eqradius, polradius, mass, ecc, axis, period)
 
 The list of Solar System planets, from Mercury to Pluto, is available
 with ``AstroLib.planets`` dictionary. The keys of this dictionary are the
 lowercase names of the planets. For example:
 
-.. code:: julia
+.. code-block:: julia
 
     julia> AstroLib.planets["mercury"]
     Planet:            Mercury
@@ -182,13 +191,13 @@ Every function provided has detailed documentation that can be
 `accessed <http://docs.julialang.org/en/stable/manual/documentation/#accessing-documentation>`__
 at Julia REPL with
 
-.. code:: julia
+.. code-block:: julia
 
     julia> ?FunctionName
 
 or with
 
-.. code:: julia
+.. code-block:: julia
 
     julia> @doc FunctionName
 

src/common.jl

@@ -7,16 +7,28 @@ List of locations of North Magnetic Pole since 1590.
 This is provided by World Magnetic Model
 (https://www.ngdc.noaa.gov/geomag/data/poles/NP.xy).
 """
-POLELATLONG = Dict{AbstractFloat,Tuple{AbstractFloat,AbstractFloat}}()
-let
-    local polelatlong, rows
-    polelatlong = readdlm(joinpath(dirname(@__FILE__), "..", "deps", "NP.xy"))
-    rows = size(polelatlong, 1)
-    for i = 1:rows
-        merge!(POLELATLONG, Dict(polelatlong[2rows + i]=>
-                                 (polelatlong[rows + i], polelatlong[i])))
+const POLELATLONG =
+    try
+        let
+            local polelatlong, rows, floattype, temp
+            polelatlong = readdlm(joinpath(dirname(@__FILE__),
+                                           "..", "deps", "NP.xy"))
+            rows = size(polelatlong, 1)
+            floattype = typeof(polelatlong[1])
+            temp = Dict{floattype, Tuple{floattype, floattype}}()
+            for i = 1:rows
+                merge!(temp, Dict(polelatlong[2rows + i]=>
+                                  (polelatlong[rows + i],
+                                   polelatlong[i])))
+            end
+            temp
+        end
+    catch
+        warn("""Could not find file NP.xy, you will not be able to use
+"geo2mag" and "mag2geo" functions.  Build again the package with
+    Pkg.build("AstroLib")
+then restart Julia session in order to fix this problem.""")
     end
-end
 
 const AU = 1.495978707e11 # Astronomical unit in meters
 const J2000 = jdcnv(2000, 01, 01, 12) # 2451545