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On 04/01/2013 15:30, And Rosta wrote:
> Jörg Rhiemeier, On 04/01/2013 13:18:


>>
>> I have been maintaining for long that RPN is a word
>> order type in itself that is actually very different
>> from the SOV word order found in about one half of all
>> human languages.
>
> Why is it actually very different? RPN has consistent
> dependent--head ordering,

If by head you mean 'operator 'and by dependent you mean
'operand'.  Let us be clear that RPN is a method which was
developed for both unambiguous mathematical expression and
for their evaluation.  It was to avoid the artificial
convention of what we used to call BODMAS when I was at
school and, indeed, the need for ever using brackets within
an expression.

Though strictly speaking it was the so-called "Polish
notation" (PN) devised by  Jan Łukasiewicz that was devised
to achieve this.  In this operator comes first and the
operands follow.  However, it was noticed by computer
scientists that if you did things the other way round, then
the expression could be built up using a stack and
immediately evaluated, which is why RPN became so widely
used in computing.

(Strictly RPN is not the reverse of PN, as the operands are
still put in the same order, e.g. "5 - 2" is "- 5 2" in PN
and "5 2 -" in RPN - not "2 5 -").

So does that mean all SOV languages are expressed as RPN,
and all VSO languages as PN?  Certainly not.

> and S & O are normally considered dependents of head V.

Yes.  If we spoke with nothing more complicated than "man
bites dog", then indeed "bites man dog" is PN, and "man dog
bites" is RPN.

The trouble us we humans like to add a few adjectives around
the place, together with maybe the odd determiner or two; we
even stick in an adverb or two and maybe one or more dratted
prepositional and/or postpositional phrases; then we have
the temerity to add relative clauses and various other
subordinate clause, etc.

I cannot think of any natlang that conforms solely to PN or
RPN ordering.

But let us take a simple RPN example. First we'll have to
recast it so that operators are replaced by a verb in such a
way that the first operand is a grammatical subject and the
second an object.  I must confess I haven't found a neat way
of doing this.  The best I can manage is to have the
operators as passive verbs; this allows the first operand to
be the subject of the verb; the second operand is then the
object of "by" or, if you prefer, the verbal phrase.

Thus I rephrase "5 2 -" as: five two diminished-by.

OK. Here is a pretty simple RPN expression:
three five augmented-by seven two diminished-by multiplied-by.

Which you easily evaluate as 40!  Or not?

[snip]

>> Who will ever become fluent in a stack-based language?
>>  Such beasts are outside what the human language
>> facility can cope with in real time, I think.

I agree.

>> Stack-based grammars are very economical with regard to
>> rules (which is the reason they are sometimes used in
>> computing), but require a prodigious short- term memory
>> in order to handle the stack properly (which computers
>> of course have).

I also agree with this.

> I don't want to repeat the several lengthy threads on
> this topic that appear to have left no impression on
> Joerg's memory,

On the contrary, I can assure you that they have left an
impression both on Jörg's mind and on mine.

> so let me essay a quick summary for Gary's benefit:
>
> The available evidence (i.e. what has been adduced in
> previous discussions) indicates that humans parse
> natlangoid lgs using stacks.

IMO all that has been adduced is that a fairly trivial use
of stack is possibly involved in human language processing.

> So in one sense, a stack-based conlang grammar would just
> be a grammar formulated in a way that takes into account
> how sentences will be parsed, and there's nothing
> obviously unnatural about it.

I have yet to see convincing examples where a sentence
parsing of human usable language can be done solely in ways
analogous to the use of stacks as a computer data structure.

> However, previous discussion of Fith, which is a
> stack-based conlang (in the above sense) revealed that
> the language was also intended to be parsed in way that
> went straight from phonology to semantic interpretation,
> without a level of syntax:

Not sure what you mean by this.  In any case this part of
the thread is really about RPN.  Is there no syntax in the
expression "5 2 -" (five two diminished-by)?

> when the parser combined an operator and operand, the
> output would be a semantic rather than a syntactic
> object.

Obviously - that's what RPN is all about.

> This is logically independent of the stack-basedness,

Maybe - but, with respect, you're putting the cart before
the horse.  Stacks are used to evaluate RPN because it's the
obvious way to do it.  By all means use the stack for
something else if you wish.  But, as a computer scientist, I
use a stack when it is useful to do so, and some other
appropriate data structure when it is useful to do so.  Data
structures are tools.

> but the previous discussion revealed that some (Ray and
> Joerg) were using the term _stack-based_ to mean
> "stack-based and syntaxless".

No - we were both using stack-based in the way that computer
scientists and programmers use the term.

> To my mind, syntaxfulness is a necessary property of
> languagehood --

Have you ever tried writing a natural language parser?

[snip]

> In "I gave the place where tomorrow the princess the *
> bishop will crown instead of the prince a quick once
> over", by the time you hit *, the stack contains (i)
> _gave_, waiting for the direct object (_a quick once
> over_), (ii) _where_, waiting for _will_, (iii)
> _tomorrow_, waiting for _will_, (iv) _the princess_,
> waiting for _will_, (v) _the_ waiting for _bishop_ and
> for _will_.

Er?  Could you evaluate this *as a stack* beginning with "I'
and proceeding to the next word and so on?

[snip]
>
>>> I want my language to be naturalistic, and I want it
>>>  to be at least theoretically possible to become
>>> fluent in the language.
>>
>> Two strong reasons to forsake a stack-based approach!
>> Stack-based languages are not naturalistic, and you'll
>>  never become fluent in them!
>
> You (Joerg) should find an apter and less misleading term
> than "stack-based".

No - stack-based means _based_ on a stack, i.e. the stack is
the main or, as in the case of RPN, only data structure used.

> In the most literal and obvious sense of "stack-based",
> natlangs are "stack-based".

If only! That has not been my experience with natural
language processing.  Natlangs are rather more complicated.

> "Stack-based languages" in your extended sense are indeed
> not naturalistic, and indeed aren't even languages, but
> because of the syntaxlessness, not the stack-basedness.

Why is "5 2 -" syntaxless?

-- 
Ray
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