Fix recognition of float and double literals of the form ".0" and "0."

CHANGELOG.md

@@ -5,6 +5,18 @@ This project adheres to [Semantic Versioning](http://semver.org/) and
 [Keep a CHANGELOG](http://keepachangelog.com).
 
 
+## Unreleased
+
+### Fixed
+
+- strings of the form `".0"` and `"0."` weren't recognized as valid XSD float  
+  and double literals
+ 
+
+[Compare v0.9.2...HEAD](https://github.com/rdf-elixir/rdf-ex/compare/v0.9.2...HEAD)
+
+
+
 ## 0.9.2 - 2021-01-06
 
 ### Added

lib/rdf/xsd/datatypes/double.ex

@@ -46,11 +46,17 @@ defmodule RDF.XSD.Double do
   end
 
   @impl XSD.Datatype
+  def lexical_mapping(lexical, opts)
+  def lexical_mapping("." <> lexical, opts), do: lexical_mapping("0." <> lexical, opts)
+
   def lexical_mapping(lexical, opts) do
     case Float.parse(lexical) do
       {float, ""} ->
         float
 
+      {float, "."} ->
+        float
+
       {float, remainder} ->
         # 1.E-8 is not a valid Elixir float literal and consequently not fully parsed with Float.parse
         if Regex.match?(~r/^\.e?[\+\-]?\d+$/i, remainder) do

test/support/xsd_test_data.ex

@@ -141,6 +141,9 @@ defmodule RDF.XSD.TestData do
     "-1" => {-1.0e0, "-1", "-1.0E0"},
     "+01.000" => {1.0e0, "+01.000", "1.0E0"},
     "1.0" => {1.0e0, "1.0", "1.0E0"},
+    "0." => {0.0e0, "0.", "0.0E0"},
+    ".0" => {0.0e0, ".0", "0.0E0"},
+    ".0E0" => {0.0e0, ".0E0", "0.0E0"},
     "123.456" => {1.23456e2, "123.456", "1.23456E2"},
     "1.0e+1" => {1.0e1, "1.0e+1", "1.0E1"},
     "1.0e-10" => {1.0e-10, "1.0e-10", "1.0E-10"},