Open a DBF file with indexes, allowing reindexing, etc.
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 Syntax

        GT_Open(<cFile>,[<aIndex>],[<cAlias>],[<lFix>], ;
                [<lPack>],[<aStruct>]) -> cAlias

 Arguments:

      <cFile> is the name of the file to open.

      <aIndex> is an array of text strings representing
      index keys.

      <cAlias> is the alias to use if successful.

      <lFix> Rebuild the indexes ?

      <lPack> Pack the  file ?

      <aStruct> is the array defining the database
      structure if the file is to be built from scratch.

 Returns:

      cAlias

 Description:

      Open a DBF file with indexes, allowing reindexing,
      packing and returning the alias.

 Examples:

      // Open customer invoices file indexed on invoice
      // number and customer account number, returing the
      // alias of INVOICES
      IF EMPTY(GT_Open('INVS0293', ;
          {'INVS','UPPER(CUSTOMER)'},'INVOICES'))

          ? 'Error'

      ENDIF

 Source: GT_OPEN.PRG

 Author:  Martin Bryant