Repetition Operators

• A REX expression may be followed by a repetition operator in order to indicate the number of times it may be repeated.

  Note: Under Windows the operation "{X,Y}" has the syntax "{X-Y}" because Windows will not accept the comma on a command line. Also, N occurrences of an expression implies infinite repetitions but in this program N represents the quantity 32768 which should be a more than adequate substitute in real world text.

• An expression followed by the operator "{X,Y}" indicates that from X to Y occurrences of the expression are to be located. This notation may take on several forms: "{X}" means X occurrences of the expression, "{X,}" means from X to N occurrences of the expression, and "{,Y}" means from 0 (no occurrences) to Y occurrences of the expression.

• The "?" operator is a synonym for the operation "{0,1}". Read as: "Zero or one occurrence."

• The "*" operator is a synonym for the operation "{0,}". Read as: "Zero or more occurrences."

• The "+" operator is a synonym for the operation "{1,}". Read as: "One or more occurrences."

• The "=" operator is a synonym for the operation "{1}". Read as: "One occurrence."