Improve __repr__ and __str__ methods of WordMorphism

[slabbe]

The __repr__ method is not fun:

sage: WordMorphism('a->ab,b->ba')
Morphism from Words over Ordered Alphabet ['a', 'b'] to Words over Ordered Alphabet ['a', 'b']
sage: WordMorphism({0:[0,1],1:[1,0]})  
Morphism from Words over Ordered Alphabet [0, 1] to Words over Ordered Alphabet [0, 1]

One always have to use the print statement (which calls __str__) ::

sage: print WordMorphism('a->ab,b->ba')
WordMorphism: a->ab, b->ba
sage: print WordMorphism({0:[0,1],1:[1,0]})
WordMorphism: 0->01, 1->10

Also, this is ugly:

sage: sigma = WordMorphism({1:[1,2], 2:[1,3], 3:[1]})
sage: E = E1Star(sigma)                              
sage: E                                              
E_1^*(WordMorphism: 1->12, 2->13, 3->1)

The proposed solution is to change the code of __repr__ so that it behaves like the actual __str__ and change the __str__ to remove the WordMorphism: part. See examples below :

The new __repr__ method :

sage: WordMorphism('a->ab,b->ba')
WordMorphism: a->ab, b->ba
sage: WordMorphism({0:[0,1],1:[1,0]})
WordMorphism: 0->01, 1->10

The new __str__ method :

sage: print WordMorphism('a->ab,b->ba')
a->ab, b->ba

sage: sigma = WordMorphism({1:[1,2], 2:[1,3], 3:[1]})
sage: E = E1Star(sigma)                              
sage: E  
E_1^*(1->12, 2->13, 3->1)

[slabbe]

I changed #13676 to remove the dependancies (by not including new _latex_ method next to the __repr__ and __str__ methods).

I separated the patch into 3 pieces : the code changed, docfixes in sage/combinat/words, docfixes in sage/combinat/iet. It will be easier to review like that and also easier to update if future conflicts occur.

Needs review!

[jdemeyer]

Please clarify which patches need to be applied.

[slabbe]

Replying to jdemeyer:

Please clarify which patches need to be applied.

All of them, in any order.