Help: Parsing expressions with operator precedence. about funcj

[jon-hanson]

The conventional simple route is to split the mult/div operators and the add/sub operators into two separate rules, and to give the mult/div rule precedence in the grammar, e.g.:

expr = prod chainl1 addSub
prod = term chainl1 multDiv
multDiv = mult | div
addSub = add | sub

By structuring the rules this way, an expression such as:

1+2*3

will be parsed as

     expr
       |
     prod
       |
     mult
    /    \
 term    add
  |     /   \
  1   term    term
       |       |
       2       3

There is an example test grammar in the library that uses that approach here:

https://github.com/typemeta/funcj/blob/master/parser/src/test/java/org/typemeta/funcj/parser/expr/Grammar.java#L65

[kpadmasola]

thanks!