[Pascal Error] YourUnit.pas(224): E2015 Operator not applicable to this operand type

I’ve got this error when was concatinating stings to build pl/sql call. Here’s an example code: sql := ‘begin ‘ + packageName + ‘.calc_report(‘ + ‘ in_dateend=>to_date(”’+ LMRFrm.a_Date2_i + ”’,”dd/mm/yyyy”),’ + ‘ in_code_list=>”’ + LMRFrm.a_ListCat_i + ”’,’ + ‘ in_currency=>”’ + LMRFrm.a_currency + ”’,’ + ‘ in_kr=>”’ + LMRFrm.a_kr + ”’,’ + ‘ in_vseason=>”’ + […]