are there any easily stated rules for constructing statements using á?

I understand them when I read them, and most of the time when I hear them, but I can never keep things straight for all the different times such a construction is required when I'm speaking or writing myself.

Examples:
"cé leis a bhfuil lón á ithe agat?"
"le mo dheirfiúr atá lón á ithe agam."
"tá a gcuid nuachtáin á léamh acu."

I don't quite get why I can't say, "léann siad a gcuid nuachtáin." - or can I? and the á example is "fronting"...stressing who is doing the reading rather than the action (reading) being done?

Also, can the prepositional pronoun be left out of the above while retaining meaning?

This is new territory for me, but I know it's kinda fundamental and something I should well understand.

Thanks in advance.

Your examples are passive voice, progressive aspect.
"With whom lunch is being eaten by you?"
(lit.: "who with-him that is lunch to-its eating by-you"
The first two examples sound strange, me thinks.
Does one really say so?
The third example is OK:
"Their newspapers are being read by them."

Of course you can say:
"Léann siad a gcuid nuachtáin."
This is habitual: "They read their newspapers (usually, always, every day, on every Monday, etc. ...)."

And you can use progressive present, active voice:
"Tá siad ag léamh a gcuid nuachtáin = They are reading their newspapers."

In passive voice you can of course omit "agat" (= "by you").

Lars

sorry, I wasn't logged in.

... and its "a gcuid nuachtán", I think.

Lars

excellent, thanks.

Because you asked for rules of "á".
Let's summarize:
"á" is used in progressive (continuous) tenses, if a 3rd person pronoun is needed as an object.
The pronoun is replaced by the possessive adjective "a" ("his", "her", "their") because of genitive case.
The form "á" is a compound of do+a or ag+a "to-his/her/their", "at his/her/their").

Tá sé á dhéanamh = "He is to-his making" -> He is making him/it (masculine)
Tá sé á déanamh = "He is to-her making" -> He is making her/it (feminine)
Tá sé á ndéanamh = "He is to-their making" -> He is making them (plural)

This is used with pronominal objects (as above) and in some special cases:
1) if "á" is referring back to the subject.
The sentence is either passive:
Tá sé á dhéanamh (agam) = "He is to-his making (by-me)" = It is being made (by me).
Or the sentence is reflexive (with féin):
Tá sé á dhéanamh féin = "He is to-his making self" = He is making himself.
2) if "á" is referring to an additional clause with "go" or "nach":
(This is used only in Munster, I think, everywhere else simply "ag")
Tá sé á rá go ... = "He is to-its saying that ..." = He is saying that ....

If the sentence Tá sé á dhéanamh (without "agam") is active or passive only depends on context ("He is making it" or "It is being made").

I don't know if "á" is used elsewhere.

Lars

(Message edited by Lars on May 02, 2008)