Opened 12 years ago

Closed 12 years ago

#5037 closed enhancement (duplicate)

Bug fixes and new functionalities for Words library

Reported by: slabbe Owned by: slabbe
Priority: major Milestone: sage-duplicate/invalid/wontfix
Component: combinatorics Keywords:
Cc: sage-combinat Merged in:
Authors: Reviewers:
Report Upstream: Work issues:
Branch: Commit:
Dependencies: Stopgaps:

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Add to Word Morphism the following functions :

  • __add__() that merges two Word Morphisms on disjoint domain.
  • restriction(self, alphabet) that returns a new Word Morphism constructed from self by restricting the domain to Words over the given alphabet.
  • disjoint_alphabet(self), for involutions only, that returns a partition A,B,C of the alphabet s.t. self(A) = B, self(B)=A and self(C) = C.

Note : I am still not convince of those three names.

Fix in Word Morphism the following function :

  • is_involution(self) : should first check that self is an endomorphism

Fix in the following functions :

  • colored_vector : Fails on empty word.

Add in the following possibilities:

  • colored_vector : Put a label on the graphical word displayed.

Change History (3)

comment:1 Changed 12 years ago by nthiery

  • Cc sage-combinat added

comment:2 Changed 12 years ago by slabbe

This is the example of a bad ticket having many feature to fix/add. Fortunately, all of those were solved by #6519 merged in sage recently.

In fact, you can now glue word morphism together using the function extend_by :

sage: n = WordMorphism({0:1,1:0,'a':5})
sage: m = WordMorphism('a->ab,b->ba')
sage: print n.extend_by(m)
WordMorphism: 0->1, 1->0, a->5, b->ba
sage: print m.extend_by(n)
WordMorphism: 0->1, 1->0, a->ab, b->ba

You can now restrict the domain of a morphism by using restrict_domain :

sage: print n.restrict_domain([0,'a'])
WordMorphism: 0->1, a->5

You can now get the partition of the domain alphabet defined (not uniquely) by a involution :

sage: inv = WordMorphism({0:1,1:0,2:2,3:3,4:5,5:4})
sage: inv.is_involution()
sage: inv.partition_of_domain_alphabet()
({0, 4}, {1, 5}, {2, 3})

The code of is_involution first check that self is an endomorphism before comptuting the square of self, which gives a better error message :

sage: print n
WordMorphism: 0->1, 1->0, a->5
sage: n.is_involution()
TypeError                                 Traceback (most recent call last)

/home/slabbe/.sage/temp/slabbe_laptop/8706/ in <module>()

/home/slabbe/sage-4.1/local/lib/python2.6/site-packages/sage/combinat/words/morphism.pyc in is_involution(self)
    973         """
    974         if not self.is_endomorphism():
--> 975             raise TypeError, "self (=%s) is not a endomorphism"%self
    977         return (self*self).is_identity()

TypeError: self (=WordMorphism: 0->1, 1->0, a->5) is not a endomorphism

The colored vector is not broken anymore on the empty word :

sage: empty = Word(); empty
sage: empty.colored_vector()

A label can now be added to the colored vector of a word (a graphic object useful to study equations on words) :

sage: w = Word([0..10]+[10,9..0])
sage: w.colored_vector(label='a palindrome rainbow')

Hence, I recommand that this ticket be closed.

comment:3 Changed 12 years ago by mvngu

  • Milestone changed from sage-combinat to sage-duplicate/invalid/wontfix
  • Resolution set to duplicate
  • Status changed from new to closed

Closing this as a duplicate of #6519.

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