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Submitted by : (unknown) at: 2007-11-17T23:04:11-08:00 (9 years ago)
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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:

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)

\label{eq1}\left[ 2, \: 3, \: 5, \: 7, \:{11}, \:{13}, \:{17}, \:{19}, \:{2
3}, \:{29}, \:...\right](1)
Type: Stream(Integer)
axiom
filterWhile(s+->s<5, p)

\label{eq2}\left[ 2, \: 3 \right](2)
Type: Stream(Integer)

However, why should this give an error?

axiom
entries 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:

axiom
lessThan(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

\label{eq3}\left[ \right](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(s<n). But Axiom is "smart enough" to know and creates the stream even though the answer is still wrong.

axiom
lessTest(n)==
  g(s) == not(s < n)
  print(g 3)
  filterWhile(g, p)
Type: Void
axiom
lessTest(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

\label{eq4}\left[ 2, \: 3, \: 5, \: 7, \:{11}, \:{13}, \:{17}, \:{19}, \:{2
3}, \:{29}, \:...\right](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 replySeverity: serious => critical

Severity: critical => minor

minor, since one has enough time to kill the evaluation using ctrl-c

The issue pointed out by Matthias is fixed --greg, Fri, 04 Jan 2008 06:49:57 -0800 reply
It was a bug in the function macroexpandall. At that time the workaround was to compile functions via the system command )set function compile on (we did not notice it here). I just tested this workaround in an old version of Axiom (February 2005) and it cures this issue. For information, an old version of Axiom (or a recent version with the buggy macroexpandall function) compiled on gcl-2.6.8pre does not crash but silently returns.

Status: open => closed




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