Re: Incorporating comments in syntax tree?

ag129@ucs.cam.ac.uk (A. Grant) writes:
> Does anyone know of any techniques for reading comments in compiler
> input and associating them with the syntax tree [...] .


The approach I've used in the past -- admitted in desperation -- was
to include an additional type of comment which was part of the syntax.
Normal comments in the language were delimited with "(* ... *)", and
were stripped by the scanner as normal. Comments delimited with "(**
... **)" were converted into comment tokens, which were allowed at
significant points in the grammar - such as after variable
declarations. This made the grammar hugely unwieldy, but it did
work. I was slightly consoled when I discovered that Sun's Java uses a
similar (if not identical) technique. :-)


> [The most common technique I know of is to hang them from the preceding or
> following token, or if you're feeling clever, maybe a nearby control
> structure to which they seem to apply. I've never heard of a technique
> that was entirely satisfactory. -John]


Indeed. I tried this approach first. All the comments next to
variables moved up one variable. :-)


steve
--
<Steve_Kilbane@cegelecproj.co.uk>
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