Synopsis constructors for declaring preconditions and postconditions on symbols
Types
data Condition
= \follow(Symbol symbol) 
| \not-follow(Symbol symbol)
| \precede(Symbol symbol)
| \not-precede(Symbol symbol)
| \delete(Symbol symbol)
| \at-column(int column)
| \begin-of-line()
| \end-of-line()
| \except(str label)
;
Usage
import ParseTree;