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#90 coredump with infinite stream

Edit detail for #90 coredump with infinite stream revision 1 of 4

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Editor: Time: 2007/11/17 23:04:11 GMT-8
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changed:
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I understand that the following is not a smart thing to do.  Axiom should complain, but it just coredumps silently::

  !\begin{axiom}
  primes:Stream Integer := generate(nextPrime, 2)
  smallerThan(stream, n) == [ s for s in stream | s < n ]
  smallerThan(primes, 100) -- Axiom 3.0 Beta coredumps
  \end{axiom}

Matthias


The failure is unrelated to '100'. It fails with the value 5.

Tim

This is likely due to stack overflow (previously reported). The construct for smallerThan requires Axiom to test EVERY element in the stream to see if s < n. There is no reason why Axiom should complain. Axiom is not designed to be able to figure out a general formula for the nth entry of the output stream for smallerThan whose signature is:

\begin{axiom}
smallerThan: (Stream Integer, PositiveInteger) -> Stream Integer
\end{axiom}

To do what you are trying to do, do this:
\begin{axiom}
)clear all
p:Stream Integer := generate(nextPrime, 2)
filterWhile(s+->s<5, p)
\end{axiom}

However, why should this give an error?
  \begin{axiom}
  entries p
  \end{axiom}

The expected result would be the first 11 (default stream length) entries. And here is another problem:

\begin{axiom}
lessThan(n)==
  g(s)== (s < n)
  print(g(3))
  filterWhile(g, p)
lessThan(5)
\end{axiom}

The local function g is not compiled correctly because n is not passed to it. So it compiles as false for all input.  The same error occurs in the NAG version.
One  would then expect Axiom to go into an infinite loop if we use not(s$<$n). But Axiom is "smart enough" to know and creates the stream even though the answer is still wrong.

\begin{axiom}
lessTest(n)==
  g(s) == not(s < n)
  print(g 3)
  filterWhile(g, p)
lessTest(5)
\end{axiom}

This crashes::

  !\begin{axiom}
  largerThan(st,n)==[s for s in st | not(s < n)]
  largerThan(p,5)
  \end{axiom}

This one below crashes, but not for the NAG version, which gives the correct answer::

  !\begin{axiom}
  before(st, n)==filterWhile(s+-> s < n, st)
  before(p,5)
  \end{axiom}

And this also crashes (whereas it does NOT crash for NAG version, giving the correct answer).::

  !\begin{axiom}
  lessThan(n)==filterWhile(s+-> (s < n), p)
  lessThan(5)
  \end{axiom}

William

From unknown Wed Feb 9 07:04:50 -0600 2005
From: 
Date: Wed, 09 Feb 2005 07:04:50 -0600
Subject: 
Message-ID: <20050209070450-0600@page.axiom-developer.org>

I understand that smallerThan in the original version does not work (I hoped it would return a stream as filterWhile does).  However, instead of coredumping silently (and taking the whole Axiom session with it), Axiom should say something like "stack limit reached in function suchandsuch" and return "failed" or something.

From unknown Tue Mar 22 20:09:15 -0600 2005
From: 
Date: Tue, 22 Mar 2005 20:09:15 -0600
Subject: property change
Message-ID: <20050322200915-0600@page.axiom-developer.org>

Severity: serious => critical

I understand that the following is not a smart thing to do. Axiom should complain, but it just coredumps silently:

  \begin{axiom}
  primes:Stream Integer := generate(nextPrime, 2)
  smallerThan(stream, n) == [ s for s in stream | s < n ]
  smallerThan(primes, 100) -- Axiom 3.0 Beta coredumps
  \end{axiom}

Matthias

The failure is unrelated to 100. It fails with the value 5.

Tim

This is likely due to stack overflow (previously reported). The construct for smallerThan requires Axiom to test EVERY element in the stream to see if s < n. There is no reason why Axiom should complain. Axiom is not designed to be able to figure out a general formula for the nth entry of the output stream for smallerThan whose signature is:

axiom
smallerThan: (Stream Integer, PositiveInteger) -> Stream Integer

Type: Void

To do what you are trying to do, do this:

axiom)clear all
   All user variables and function definitions have been cleared.
p:Stream Integer := generate(nextPrime, 2)

(1)

Type: Stream Integer

axiom
filterWhile(s+->s<5, p)

(2)

Type: Stream Integer

However, why should this give an error?

axiomentries p
   >> Error detected within library code:
   infinite stream

The expected result would be the first 11 (default stream length) entries. And here is another problem:

axiomlessThan(n)==
  g(s)== (s < n)
  print(g(3))
  filterWhile(g, p)

Type: Void

axiom
lessThan(5)

axiom

Compiling function g with type PositiveInteger -> Boolean

axiom

Compiling function g with type Integer -> Boolean

axiom

Compiling function lessThan with type PositiveInteger -> Stream 
      Integer 
   false

(3)

Type: Stream Integer

The local function g is not compiled correctly because n is not passed to it. So it compiles as false for all input. The same error occurs in the NAG version. One would then expect Axiom to go into an infinite loop if we use not(sn). But Axiom is "smart enough" to know and creates the stream even though the answer is still wrong.

axiomlessTest(n)==
  g(s) == not(s < n)
  print(g 3)
  filterWhile(g, p)

Type: Void

axiomlessTest(5)
   Compiled code for g has been cleared.
   Compiled code for lessThan has been cleared.
   1 old definition(s) deleted for function or rule g

axiom

Compiling function g with type PositiveInteger -> Boolean

axiom

Compiling function lessTest with type PositiveInteger -> Stream 
      Integer 
   true

axiom

Compiling function g with type Integer -> Boolean

(4)

Type: Stream Integer

This crashes:

  \begin{axiom}
  largerThan(st,n)==[s for s in st | not(s < n)]
  largerThan(p,5)
  \end{axiom}

This one below crashes, but not for the NAG version, which gives the correct answer:

  \begin{axiom}
  before(st, n)==filterWhile(s+-> s < n, st)
  before(p,5)
  \end{axiom}

And this also crashes (whereas it does NOT crash for NAG version, giving the correct answer).:

  \begin{axiom}
  lessThan(n)==filterWhile(s+-> (s < n), p)
  lessThan(5)
  \end{axiom}

William

...: Wed, 09 Feb 2005 07:04:50 -0600 reply

I understand that smallerThan in the original version does not work (I hoped it would return a stream as filterWhile does). However, instead of coredumping silently (and taking the whole Axiom session with it), Axiom should say something like "stack limit reached in function suchandsuch" and return "failed" or something.

property change

Tue, 22 Mar 2005 20:09:15 -0600 reply

Severity: serious => critical