Convert an array into a character string
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 Syntax

        GT_a2Str(<aData>,<bConvert>,<nLength>) -> cData

 Arguments:

      <aData> is the array of data. <bConvert> must be
      able to handle all data types found in the array.

      <bConvert> is the Block function to convert the data
      from the array. This data will then be padded to
      <nLength> by the GT_a2Str().

      <nLength> is the length to pad the items to in the
      string.

 Returns:

      cData

 Description:

      To turn an array into a character string, for saving to a
      mem file etc.

 Examples:

      // Convert number  array to a string.
      aData := {0,2,7,51,9,4}
      cData := GT_a2Str(aData,{ | nVal | Str(nVal) },2)
      // Result is " 0 2 751 9 4"

 Source: GT_A2STR.PRG

 Author:  Martin Bryant