add FormulaTokenArray::ReplaceToken()

Change-Id: I42c893677c1b8a35ee502a9ae438d4c0f19867d3

formula/source/core/api/token.cxx

@@ -849,6 +849,24 @@ FormulaToken* FormulaTokenArray::MergeArray( )
     return NULL;
 }
 
+FormulaToken* FormulaTokenArray::ReplaceToken( sal_uInt16 nOffset, FormulaToken* t )
+{
+    if (nOffset < nLen)
+    {
+        CheckToken(*t);
+        sal_uInt16 nPos = nLen - nOffset - 1;
+        t->IncRef();
+        pCode[nPos]->DecRef();
+        pCode[nPos] = t;
+        return t;
+    }
+    else
+    {
+        t->Delete();
+        return NULL;
+    }
+}
+
 FormulaToken* FormulaTokenArray::Add( FormulaToken* t )
 {
     if( !pCode )

include/formula/tokenarray.hxx

@@ -115,6 +115,10 @@ protected:
 
     /// Also used by the compiler. The token MUST had been allocated with new!
     FormulaToken*           Add( FormulaToken* );
+    /** Also used by the compiler. The token MUST had been allocated with new!
+        @param nOffset negative offset of token, 0==last, 1==previous, ...
+     */
+    FormulaToken*           ReplaceToken( sal_uInt16 nOffset, FormulaToken* );
     inline  void            SetCombinedBitsRecalcMode( ScRecalcMode nBits )
                                 { nMode |= (nBits & ~RECALCMODE_EMASK); }
     inline  ScRecalcMode    GetCombinedBitsRecalcMode() const