Change log for Magma V2.13-11 (Released 5/4/2007)

Algebraic Geometry

·A bug in pullbacks by maps between curves has been fixed. Reported by B. Smith.

·Several redundant subset intrinsics have been removed. This fixes an ambiguous signature match when testing whether an indexed set of points is contained in a scheme. Reported by B. Smith.

·A bug in the parametrisation of rational plane curves has been fixed.

·A bug in ShortBasis for divisors on curves has been fixed. Reported by M. Grassl

Algebras

·The action of a matrix on an element of a free algebra or quotient thereof now works properly. Bug reported by E. Rains.

Coding Theory

·A bug that caused at most one cyclic generator matrix to be used during minimum weight computations has been fixed. Reported by M. Grassl.

·HasLinearGrayMapImage now works for the zero code. Bug reported by M. Villanueva.

·A bug that caused the results of GriesmerMinimumWeightBound to be too high has been fixed. Reported by M. Kiermaier.

Commutative Algebra

·The Hilbert polynomial/series functions have been speeded up. This affects several other functions, like Degree for projective schemes.

Elliptic Curves

·The code for IsDivisibleBy or DivisionPoints as applied to a point in the kernel of reduction of an elliptic curve over a p-adic field has been updated. There is now a much smaller loss in precision if all division points are required and some exist which do not reduce to 0.

·Point functions IsWeaklyEqual and IsWeaklyZero have been added. These test for weak equality/nullity of points over a variable precision p-adic field. Over an exact field, they are the usual equality/zero checks.

Graded Rings

·A bug in the printing of graded rings has been fixed. Reported by B. Smith.

Groups

·A bug in IsConjugate for two elements of a pc-group, when the elements are not contained in the conjugating group, has been fixed. An incorrect conjugating element was being returned.

·A bug computing image and kernel of a group homomorphism when the codomain is not a permutation or matrix group has been fixed. Reported by Eamonn O'Brien.

·A bug when computing MaximalSubgroups of Alt(49) has been fixed. Bug report from Colva Roney-Dougal, fix by Derek Holt.

·A crash when Subgroups is called on a PC-group with parameter OrderEqual set to a non-divisor of the group order has been fixed.

Integers

·A bug that caused a crash when ECPP fails has been fixed.

Lattices

·The function IsIsometric has been fixed so that it does not crash or return an incorrect answer when only a proper isometric embedding is found.

Matrices

·The functions Submatrix, Pfaffian and Minor may now take index sequences specifying submatrices.

Module Theory

·A bug in decomposition of algebras has been fixed. Reported by D. Gruenewald.

Number Fields

·A bug in NormEquation over number fields that would, in certain trivial cases, trigger a runtime error, has been fixed.

·A bug in Completion of number fields that could in certain cases cause runtime errors has been fixed.

Polynomial Rings

·A bug in multiplication in polynomial quotient rings over integer residue rings has been fixed. Reported by H. Hubrechts.

·A crash in the factorization of the polynomial 1 over function fields has been fixed. Reported by F. Hess.

·A coercion problem in Evaluate has been fixed. Reported by E. Rains.

System

·Added a %O format code to the various printf-style directives and intrinsics. This enables a print level to be specified for the object. e.g., printf "%O\n", X, "Minimal";