Order of elements in visitor for AT_LEAST_ONE rule

[dhowe]

So I have a parser rule which allows combinations of choice and symbol in any order:

    $.RULE("expr", () => {
      $.AT_LEAST_ONE(() => {
        $.OR([
          { ALT: () => $.SUBRULE($.choice) },
          { ALT: () => $.SUBRULE($.symbol) },
        ])
      })
    })

Assuming I have an expression that consists of both a choice and a symbol, I am wondering the best way for my visitor to determine which came first in the input string?

The ctx argument passed to my visit method is an object with both choice and symbol as keys, but these are unordered.

I could drill down to the location property which refers back to the input string, but I'm guessing there's a better way?

[bd82]

Hello @dhowe

If you wrap the alternation:

        $.OR([
          { ALT: () => $.SUBRULE($.choice) },
          { ALT: () => $.SUBRULE($.symbol) },
        ])

in its own rule (lets name it "expElement") and invoke that rule from the "loop":

    $.RULE("expr", () => {
      $.AT_LEAST_ONE(() => {
          $.SUBRULE($.expElement)
      })
    })

You will get an orderedList back, at the cost of another level of nesting...

[dhowe]

that's great, thanks