changes, 1.6

packages that have been published and certified:
- VersalDeformations, a package for calculating tangent and obstruction spaces as well as power series solutions for deformation problems involving isolated singularities and projective schemes, has been published.
- KustinMiller, a package for unprojection and the Kustin-Miller complex, has been published.
new packages:
- PushForward, a package for computing the push-forward functor for finite ring maps, has been added. (It should have been added to the previous distribution.)
- EliminationMatrices, a package for computing resultants, has been added.
- EllipticIntegrals, a package for numerical computation of elliptic integrals and elliptic functions, has been added.
- Triplets, a package for computing Betti diagrams and hypercohomology tables associated to triplets of degree sequences, has been added.
- CompleteIntersectionResolutions, a package for analyzing the asymptotic structure of minimal resolutions over a complete intersection, has been added.
improved packages:
- The package GraphicalModels has been extended significantly by its authors. The previous version of this package was simply a basic extension of the package Markov. Among the new algorithms implemented are procedures for computing the vanishing ideal of a graphical model and for checking for identifiable parameters in Gaussian mixed graph models. These procedures can be used to study fundamental problems about graphical models.
- The package Schubert2 now handles intersection rings of isotropic flag bundles, with an algorithm based on a theorem in a paper of Grayson, Seceleanu, and Stillman.
functionality added or improved:
- Factoring of polynomials over non-prime Galois fields has been added, using the Singular-Factory library.
- The methods for Hom(Matrix,Module) and Hom(Module,Matrix) now handle non-free modules. There is also a new method for Hom(Matrix,Matrix).
functionality changed:
- changed the order of loading packages inside a package, as specified by newPackage(...,PackageImports=>...) and newPackage(...,PackageExports=>...) options, so that the order of loading is easy to specify (to avoid problems with shadowed variables). The packages are loaded with needsPackage, and now the imported packages are loaded before the exported packages. So, if there is a problem, just replicate all the exported packages in the list of imports, and juggle the order of the list of imports.
- The function temporaryFileName now obeys the TMPDIR environment variable, the way other unix applications do, rather than putting temporary files into the directory /tmp.
new constants and operators:
- New functions fileReadable, fileWritable, fileExecutable provide information about file permissions.
- The class Task replaces Thread, and the function isCanceled tells whether a task has been canceled.