patch formula parsing.

#92 many thanks to @alexei-lexx for not only finding this, but taking time to report the problem.

3 files changed, 12 insertions, 1 deletions

diff --git a/lib/axlsx.rb b/lib/axlsx.rb
index 6fce32b5..6e8f4e23 100644
--- a/lib/axlsx.rb
+++ b/lib/axlsx.rb
@@ -54,6 +54,7 @@ module Axlsx
     ref
   end
 
+  # returns the x, y position of a cell
   def self.name_to_indices(name)
     raise ArgumentError, 'invalid cell name' unless name.size > 1
     v = name[/[A-Z]+/].reverse.chars.reduce({:base=>1, :i=>0}) do  |val, c|
diff --git a/lib/axlsx/workbook/worksheet/cell.rb b/lib/axlsx/workbook/worksheet/cell.rb
index 91efa8d9..c58ede3a 100644
--- a/lib/axlsx/workbook/worksheet/cell.rb
+++ b/lib/axlsx/workbook/worksheet/cell.rb
@@ -296,7 +296,7 @@ module Axlsx
       when :string
         #parse formula
         if @value.start_with?('=')
-          str  << 't="str"><f>' << @value.to_s.gsub('=', '') << '</f>'
+          str  << 't="str"><f>' << @value.to_s.sub('=', '') << '</f>'
         else
           #parse shared
           if @ssti
diff --git a/test/workbook/worksheet/tc_cell.rb b/test/workbook/worksheet/tc_cell.rb
index edb3ae85..6a93fc58 100644
--- a/test/workbook/worksheet/tc_cell.rb
+++ b/test/workbook/worksheet/tc_cell.rb
@@ -251,6 +251,16 @@ class TestCell < Test::Unit::TestCase
     assert_equal(c_xml.xpath("/c[@s=1]").size, 1)
   end
 
+  def test_to_xml_string_formula
+    p = Axlsx::Package.new
+    ws = p.workbook.add_worksheet do |ws|
+      ws.add_row ["=IF(2+2=4,4,5)"]
+    end
+    doc = Nokogiri::XML(ws.to_xml_string)
+    assert("//f[text()=['IF(2+2=4,4,5)']")
+
+  end
+
   def test_to_xml
     # TODO This could use some much more stringent testing related to the xml content generated!
     row = @ws.add_row [Time.now, Date.today, true, 1, 1.0, "text", "=sum(A1:A2)"]