Top-down operator precedence parsing

Learning about Pratt parsing. (A similar, if not the same, technique is used to parse Mercury terms, and is presumably common to Prolog systems.)

The toy grammar implemented is:

e --> NAME
    ; INTEGER
    ; name = e
    ; e ? e : e
    ; prefixop e
    ; e postfixop
    ; e infixop e
    ; e ( args )
    ; ( e )

args --> zero or more comma-separated e

prefixop --> + ; - ; !

postfixop --> !

infixop --> + ; - ; * ; / ; ^ ; < ; >

where < and > are non-associative.

This is a better introduction than most: Pratt Parsers: Expression Parsing Made Easy

Author

Peter Wang novalazy@gmail.com