Syntactic categories

PGE's operator precedence parser understands the following syntactic categories:

term:             # 1, 'hello'
infix:            # infix:<+>, infix:<&>, infix:<=>
prefix:           # prefix:<++>, prefix:<->, prefix:<!>
postfix:          # postfix:<++>, postfix:<-->
circumfix:        # circumfix:<( )>
postcircumfix:    # postcircumfix:<[ ]>
ternary:          # ternary:<? :>