Precedence

Precedence indicates the priority of a certain delimiter, relative to the other delimiters. Precedence is used to resolve delimiter conflicts when one delimiter is a copy or prefix of another. In case of equal precedence, the innermost prevails.

By default, all delimiters are at precedence 10, which means they are all considered the same; fixed fields are hard-coded at precedence 10. Delimiters on parent nodes are not considered when parsing the child fields; only the child’s delimiter (or if it is a fixed field, its length). The range of valid precedence values is from 1 to 100, inclusive. The higher the value, the higher the precedence. Delimiters with higher precedence have a greater chance to be matched.

Changing the precedence of a delimiter will cause it to be applied to the input data-stream in different ways. For example:

• root

  • element (type delim, delimiter = “^”, repeat)

  • field_1 (type fixed, length = 5)

  • field_2 (type fixed, length = 8, optional)

    Although this will parse ”abcde12345678^zyxvuABCDEFGH’, it will not parse the text ”abcde^zyxvuABCDEFGH’ even though the second fixed field is optional. The reason is that the element’s delimiter is ignored within the fixed field because they have the same precedence. If you want the element’s delimiter to be examined within the fixed field data, you must change its precedence, for example:

  root

  • element (type delim, delimiter = “^”, repeat, precedence = 11)

  • field_1 (type fixed, length = 5)

  • field_2 (type fixed, length = 8, optional)

    This will successfully parse the text ”abcde^zyxvuABCDEFGH’.

    A similar argument can be applied to delimited child nodes. The parser normally attempts to match the child delimiter— setting the precedence to 11 forces the parser to match the parent delimiter first.