9e216da9ef
After go1.16, go will use module mode by default, even when the repository is checked out under GOPATH or in a one-off directory. Add go.mod, go.sum to keep this repo buildable without opting out of the module mode. > go mod init github.com/mmcgrana/gobyexample > go mod tidy > go mod vendor In module mode, the 'vendor' directory is special and its contents will be actively maintained by the go command. pygments aren't the dependency the go will know about, so it will delete the contents from vendor directory. Move it to `third_party` directory now. And, vendor the blackfriday package. Note: the tutorial contents are not affected by the change in go1.16 because all the examples in this tutorial ask users to run the go command with the explicit list of files to be compiled (e.g. `go run hello-world.go` or `go build command-line-arguments.go`). When the source list is provided, the go command does not have to compute the build list and whether it's running in GOPATH mode or module mode becomes irrelevant.
103 lines
2.4 KiB
Plaintext
103 lines
2.4 KiB
Plaintext
/*++ $Id: AlternatingGroup.mu,v 1.4 2003/09/08 15:00:47 nthiery Exp $
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Dom::AlternatingGroup(n) -- the Alternating Group of {1..n}
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n - integer >= 1
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Elements are represented as in Dom::PermutationGroup(n)
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Author: Nicolas M. Thiéry <nthiery@users.sourceforge.net>
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License: LGPL
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Created: August 8th, 1999
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Last update: $Date: 2003/09/08 15:00:47 $
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++*/
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domain Dom::AlternatingGroup(n: Type::PosInt)
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inherits Dom::PermutationGroup(n,toBeDefined);
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category Cat::PermutationGroup;
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axiom Ax::canonicalRep;
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/*--
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size
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Size of the group.
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--*/
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size := fact(n)/2;
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/*--
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generators
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A list of generators of the group
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The first 3-cycle (1,2,3), and a maximal even cycle (1,...,n) or
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(2,...,n) depending on the parity of n
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--*/
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generators :=
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if n<=2 then generators:=[dom([[1]])];
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elif n=3 then generators:=[dom([[1,2,3]])];
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elif n mod 2=0 then generators:=[dom([[1,2,3]]), dom([[$2..n]])];
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else generators:=[dom([[1,2,3]]), dom([[$1..n]])];
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end_if;
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/*--
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allElements
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List of all the elements of the group
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--*/
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allElements :=
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proc()
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option remember;
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local p;
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begin
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[new(dom,p) $ p in select(combinat::permutations(n),
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p->bool(combinat::permutations::sign(p)=1))];
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end_proc;
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/*--
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cycleTypes:
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Count the elements of the group by cycle type.
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(Cf Cat::PermutationGroupModule).
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Same algorithm as for Dom::SymmetricGroup, but only even permutations
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are considered. This is done by disregarding partitions p such
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that n-length(p) is odd.
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--*/
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cycleTypes :=
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proc()
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option remember;
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local t, p, gen;
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begin
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userinfo(3, "cycleTypes: starting computation");
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t:=table();
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gen := combinat::partitions::generator(n);
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while (p:=gen()) <> FAIL do
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userinfo(5, "working on partition", p);
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if(n-nops(p) mod 2=0) then
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// Compute the size of the conjugacy class of Sn indexed by p
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// and the cycle type of a permutation in this conjugacy class
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t[combinat::partitions::toExp(p,n)]
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:= combinat::partitions::conjugacyClassSize(p);
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end_if;
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end_while;
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t;
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end_proc;
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begin
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if testargs() then
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if args(0) <> 1 then error("wrong no of args"); end_if;
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if not testtype(n,DOM_INT) then
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error("argument must be integer")
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end_if;
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if n < 1 then
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error("argument must be positive")
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end_if;
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end_if;
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end_domain:
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