From c85846b7a02b72c8f6f4df63dced5ee10fadd2bd Mon Sep 17 00:00:00 2001
From: u2 <zhangyaning1985@gmail.com>
Date: Sat, 11 Jan 2014 10:56:07 +0800
Subject: [PATCH] Add String#is_number? method

---
 lib/core/facets/string.rb        |  1 +
 lib/core/facets/string/number.rb | 14 ++++++++++
 test/core/string/test_number.rb  | 44 ++++++++++++++++++++++++++++++++
 3 files changed, 59 insertions(+)
 create mode 100644 lib/core/facets/string/number.rb
 create mode 100644 test/core/string/test_number.rb

diff --git a/lib/core/facets/string.rb b/lib/core/facets/string.rb
index b6d89b08..35f43a87 100644
--- a/lib/core/facets/string.rb
+++ b/lib/core/facets/string.rb
@@ -32,6 +32,7 @@
 require_relative 'string/natcmp.rb'
 require_relative 'string/nchar.rb'
 require_relative 'string/newlines.rb'
+require_relative 'string/number.rb'
 require_relative 'string/op_div.rb'
 require_relative 'string/op_sub.rb'
 require_relative 'string/outdent.rb'
diff --git a/lib/core/facets/string/number.rb b/lib/core/facets/string/number.rb
new file mode 100644
index 00000000..2942cee2
--- /dev/null
+++ b/lib/core/facets/string/number.rb
@@ -0,0 +1,14 @@
+class String
+
+  # Returns true if it's a decimal digits.
+  #
+  #   "123_456_789_123_456_789.123_456_000_111".number?  # => true
+  #   "1.23".number?  # => true
+  #   "1.23a".number? # => false
+  #
+  # CREDIT: u2
+
+  def number?
+    !!self.match(/\A[+-]?\d+?(_?\d+?)*?(\.\d+(_?\d+?)*?)?\Z/)
+  end
+end
\ No newline at end of file
diff --git a/test/core/string/test_number.rb b/test/core/string/test_number.rb
new file mode 100644
index 00000000..2d7b9bdd
--- /dev/null
+++ b/test/core/string/test_number.rb
@@ -0,0 +1,44 @@
+covers 'facets/string/number'
+
+test_case String do
+
+  method :number? do
+
+    test do
+      x = "1.23\n"
+      x.number?.assert == true
+    end
+
+    test do
+      x = "123_456_789_123_456_789.123_456_000_111\n"
+      x.number?.assert == true
+    end
+
+    test do
+      x = ".123\n"
+      x.number?.assert == false
+    end
+
+    test do
+      x = "123_\n"
+      x.number?.assert == false
+    end
+
+    test do
+      x = "_123\n"
+      x.number?.assert == false
+    end
+
+    test do
+      x = "23_456_789_123_456_.245\n"
+      x.number?.assert == false
+    end
+
+    test do
+      x = "23_456_789_123_456._245\n"
+      x.number?.assert == false
+    end
+
+  end
+
+end
\ No newline at end of file