Added Literal#squish and #squish! to remove leading/trailing whitespa…

…ce and multiple internal whitespace characters from the value of a literal.

lib/rdf/model/literal.rb

@@ -408,6 +408,30 @@ def canonicalize!
       self
     end
 
+    ##
+    # Returns the literal, first removing all whitespace on both ends of the value, and then changing remaining consecutive whitespace groups into one space each.
+    #
+    # Note that it handles both ASCII and Unicode whitespace.
+    #
+    # @see [String#squish](http://apidock.com/rails/String/squish)
+    # @return [RDF::Literal] a new literal based on `self`.
+    def squish(*other_string)
+      self.dup.squish!
+    end
+
+    ##
+    # Performs a destructive {#squish}.
+    #
+    # @see [String#squish!](http://apidock.com/rails/String/squish%21)
+    # @return self
+    def squish!
+      @string = value.
+        gsub(/\A[[:space:]]+/, '').
+        gsub(/[[:space:]]+\z/, '').
+        gsub(/[[:space:]]+/, ' ')
+      self
+    end
+
     ##
     # Escape a literal using ECHAR escapes.
     #

spec/model_literal_spec.rb

@@ -248,7 +248,6 @@ def self.literals(*selector)
     end
   end
 
-
   describe "#compatible?" do
     {
       %("abc") => {
@@ -286,6 +285,32 @@ def self.literals(*selector)
     end
   end
 
+  describe "#squish" do
+    let(:result) {"a b c"}
+    subject {RDF::Literal("  a\n b  c\n  ")}
+
+    it "squeezes properly" do
+      expect(subject.squish).to eq result
+    end
+
+    it "returns a new object" do
+      expect(subject.squish).not_to equal subject
+    end
+  end
+
+  describe "#squish!" do
+    let(:result) {"a b c"}
+    subject {RDF::Literal("  a\n b  c\n  ")}
+
+    it "squeezes properly" do
+      expect(subject.squish!).to eq result
+    end
+
+    it "returns itself" do
+      expect(subject.squish!).to equal subject
+    end
+  end
+
   describe RDF::Literal::Boolean do
     it_behaves_like 'RDF::Literal with datatype and grammar', "true", RDF::XSD.boolean
     it_behaves_like 'RDF::Literal equality', "true", true