GAP 4.4 Update 5 (May 2005)

Errors listed in bold may cause the system to return a wrong result without issuing a warning, errors in italics can cause a system crash. Other errors typically will lead to an error message and may cause the abortion of a run but will not cause wrong results.

Fixed bugs

1. GroupWithGenerators returned a meaningless group object instead of signaling an error when it was called with an empty list of generators.
2. A rare problem with the choice of prime in the Dixon-Schneider Algorithm for computing the character table of a group. [Reported by Jack Schmidt]
3. DirectProduct for trivial permutation groups returned a strange object.
4. When computing preimages under an embedding into a direct product of permutation groups, if the element was not in the image of the embedding then a permutation had been returned instead of fail.
5. A problem with PolynomialReduction running into an infinite loop.
6. Adding linear mappings with different image domains was not possible. [Reported by Pasha Zusmanovich]
7. Multiplying group ring elements with rationals was not possible. [Reported by Laurent Bartholdi]
8. Random now works for finite fields of size larger than 2²⁸. [Reported by Jack Schmidt]
9. Two problems with PowerMod for polynomials. [Reported by Jack Schmidt]
10. Univariate polynomial creators did modify the coefficient list passed. [Reported by Juergen Mueller]
11. Some methods for computing the sum of ideals returned the first summand instead of the sum. [Reported by Alexander Konovalov]
12. Some code and comments in the GAP kernel assumed that there is no garbage collection during the core printing function Pr, which is not correct. This could cause GAP in rare cases to crash during printing permutations, cyclotomics or strings with zero bytes. [Reported by Warwick Harvey]
13. Fixed IntHexString to accept arguments not in IsStringRep; the argument is now first converted if necessary. [Reported by Kenn Heinrich]
14. Wrong result in Intersection for PC groups.
15. The function CompareVersionNumbers erroneously ignored leading non-digit characters.
    A new feature in the corrected version is an optional third argument "equal", which causes the function to return true only if the first two arguments describe equal version numbers; documentation is available in the ext-manual. This new feature is used in LoadPackage, now one can require a specific version of a package.
    The library code still contained parts of the handling of completion files for packages, which does not work and therefore had already been removed from the documentation. This code has now been removed.
    Now a new component PreloadFile is supported in PackageInfo.g files; if it is bound then the file in question is read immediately before the package or its documentation is loaded.
16. The library code for stabilizer chains contained quite some explicit references to the identity (). This is unfortunate if one works with permutation groups, the elements of which are not plain permutations but objects which carry additional information like a memory, how they were obtained from the group generators. For such cases it is much cleaner to use the One(...) operation instead of (), such that the library code can be used for a richer class of group objects. This fix contains only rather trivial changes () to One(...) which were carefully checked by me. The tests for permutation groups all run without a problem. However, it is relatively difficult to provide test code for this particular change, since the "improvement" only shows up when one generates new group objects. This is for example done in the package recog which is in preparation. [Reported by Akos Seress and Max Neunhoeffer]
17. Using {} to select elements of a known inhomogenous dense list produced a list that might falsely claim to be known inhomogenous, which could lead to a segfault if the list typing code tried to mark it homogenous, since the code intended to catch such errors also had a bug. [Reported by Steve Linton]
18. The record for the generic iterator construction of subspaces domains of non-row spaces was not complete.
19. The result of String for strings not in IsStringRep that occur as list entries or record components was erroneously missing the doublequotes around the strings.
20. This bug causes InducedPcgs(pcgs, H) to return a pcgs which is not induced wrt. the parent pcgs of pcgs. This may cause unpredictable behaviour, e. g. when SiftedPcElement is used subsequently. [Reported by Alexander Konovalov]
21. Fixed a bug in SmallGroupsInformation(512).
22. PowerModCoeffs with exponent 1 for compressed vectors did not reduce (a copy of) the input vector before returning it. [Reported by Frank Luebeck]
23. Sorting a mutable non-plain list (e.g., a compressed matrix over fields of order < 257) could potentially destroy that object. [Reported by Alexander Hulpke]
24. When a workspace has been created without packages (-A option) and is loaded into a GAP session without packages (same option) then an error message is printed.
25. So far the functions IsPrimeInt and IsProbablyPrimeInt are essentially the same except that IsPrimeInt issues an additional warning when (non-proven) probable primes are considered as primes.
    These warnings now print the probable primes in question as well; if a probable prime is used several times then the warning is also printed several times; there is no longer a warning for some known large primes; the warnings can be switched off. See ?Ref: IsPrimeInt for more details.
    If we get a reasonable primality test in GAP we will change the definition of IsPrimeInt to do a proper test.
26. Corrected some names of primitive groups in degree 26. [Reported by Robert F Bailey]
27. Under rare circumstances computing the closure of a permutation group by a normalizing element could produce a corrupt stabilizer chain. (The underlying algorithm uses random elements, probability of failure was below 1 percent) [Reported by Thomas Breuer]

New or improved functionality

1. Several changes for ConwayPolynomial:
   • many new pre-computed polynomials
   • put data in several separate files (only read when needed)
   • added info on origins of pre-computed polynomials
   • improved performance of ConwayPolynomial and IsPrimitivePolynomial for p < 256
   • improved documentation of ConwayPolynomial
   • added and documented new functions IsCheapConwayPolynomial and RandomPrimitivePolynomial
2. Added method for NormalBase for extensions of finite fields.
3. Added more help viewers for the HTML version of the documentation (firefox, mozilla, konqueror, w3m, safari).
4. New function ColorPrompt. (Users of former versions of a colorprompt.g file: Now you just need a ColorPrompt(true); in your .gaprc file.)
5. Specialised kernel functions to support GUAVA 2.0. GAP will only load GUAVA in version at least 2.002 after this update.
6. Now there is a kernel function CYC_LIST for converting a list of rationals into a cyclotomic, without arithmetics overhead.
7. New functions ContinuedFractionExpansionOfRoot and ContinuedFractionApproximationOfRoot for computing continued fraction expansions and continued fraction approximations of real roots of polynomials with integer coefficients.
8. A method for computing structure descriptions for finite groups, available via StructureDescription.
9. This change contains the new, extended version of the SmallGroups package. For example, the groups of orders p⁴, p⁵, p⁶ for arbitrary primes p, the groups of square-free order and the groups of cube-free order at most 50000 are included now. For more detailed information see the announcement of the extended package.
10. The function ShowPackageVariables gives an overview of the global variables in a package. It is thought as a utility for package authors and referees. (It uses the new function IsDocumentedVariable.)
11. The mechanisms for testing GAP has been improved:
    • The information whether a test file belongs to the list in tst/testall.g is now stored in the test file itself.
    • Some targets for testing have been added to the Makefile in the GAP root directory, the output of the tests goes to the new directory dev/log.
    • Utility functions for testing are in the new file tst/testutil.g. Now the loops over (some or all) files tst/*.tst can be performed with a function call, and the file tst/testall.g can be created automatically; the file tst/testfull.g is now obsolete. The remormalization of the scaling factors can now be done using a GAP function, so the file tst/renorm.g is obsolete.
    • Now the functions START_TEST and STOP_TEST use components in GAPInfo instead of own globals, and the random number generator is always reset in START_TEST.
    • GAPInfo.SystemInformation now takes two arguments, now one can use it easier in the tests.
12. MultiplicationTable is now an attribute, and the construction of a magma, monoid, etc. from multiplication tables has been unified.