trotter

• Update for Dart 3.

• Null-safety migration.

• Added a Storage class to wrap other classes; this allows us to add, remove and keep track of arrangements in a memory efficient (one bit per arrangement) way. Can only be used for moderately sized structures.
• Updated the fun-with-mastermind example to make use of the storage class.

• Fixed some minor mistakes in the code.
• Added fun-with-trotter-sprites example.

• Followed some of the pub.dev health suggestions.
• Added link to Permutation Products demo.
• Corrected environment requirements (Dart 2.7.0 to support extensions).

• Added extensions to Lists and Strings. (Nice Dart 2.7.0 feature!)
• Provided functionality for random sampling from the pseudo-lists.

• Cleaned up the type declaration for the iterables.
• Link to Falco-shapes demo.

Made the abstract, parent class Combinatorics visible to the user for those cases in which the combinatorics type is not known at the time of declaration.

• Cleaned up code to be more in line with Dart 2.
• Added example.dart (and an example output, fun-with-mastermind.md) to example/.

• As of Dart 2, int instances represent 64 bit, as opposed to arbitrary length, integers. Since trotter often works with very large integers, it needed an overhaul so as to incorporate the BigInt class. This resulted in several breaking changes, most notably that the base _Combinatoric class no longer extends ListBase. I have made the class instances callable, however, to address this: code that needs an instance of one of the classes to behave like an iterable just need to call the instance. For example, if perms is an instance of Permutations, we would now use something like for (var p in perms()) (as opposed to for (var p in perms), which worked in previous versions). The instances can still be thought of as pseudo-lists in that they can be indexed and have several properties and methods that might be expected in a list, such as length and indexOf.

• I took advantage of the necessity of making breaking changes mentioned above to make one more: I have renamed the Selections class Compositions. In combinatorics literature, the term selection is often use as a generic word to mean either combination or permutation. This might have caused confusion in the way I had used the term in previous versions of the library. I think that composition is more appropriate to mean a selection in which order is not important (if a body is composed of materials A, B and C then it is also composed of materials C, B and A) and items are "replaced" (it makes sense to say that a body is composed of two parts A to one part B, for example).

• Fixed an error introduced during the changes made for 0.9.0.

• Cleaned up and simplified the code so that the structures extend Lists more naturally. (Structures extend ListBase now instead of Iterable.)
• Should be backwards compatible in that code that works in previous versions should also work in this version.
• Structures should now behave better with List methods like map, where, every and so on.

• Cleaned up the code so that the library may be used in strong mode.
• Added subset of the functionality associated with Iterables (first, last, any, every, forEach etc.). Some functionality that would be redundant (e.g. isEmpty) or less meaningful/useful (e.g. fold) neglected. Since structures we can represent can "contain" a huge number of arrangements, we need to be careful about using methods that iterate over the structures (like any, every, forEach).

• Added the Compounds class (permutations of unspecified size).
• Added the contains method for all classes.
• Corrected indexOf behavior for when arrangements that don't exist are passed as arguments; returns -1 if the arrangement is not in the pseudo-list.

• Added inverses to all the functions so that we can look up arrangements non iteratively (now possible to look up values in arbitrarily large pseudo-lists; this library was incomplete without this functionality!).
• Made the code more readable. Made a few minor tweaks to the existing code.

Improved the documentation; minor bug fixes.

First Dart release: support for classes:

• Permutations
• Combinations
• Amalgams (permutations with replacement during arranging)
• Selections (combinations with replacement during arranging)
• Subsets