Diamond brackets <> and square brackets [] notations

asked 5 years ago

petRUShka
301 ●10 ●25 ●31

updated 5 years ago

Are there some documentation on diamond bracket notation:

R.<w> = PolynomialRing(QQ)

and square bracket notation:

R.<y> = QQ['y'];

There is some documentation in Constructors for polynomial rings docs but it looks superficial on this topic.

Are there some complete explanation with all the details behind the scene?

Is it only for polynomial rings or for some other objects? Is it SageMath addition?

answered 5 years ago

Sébastien
3321 ●8 ●44 ●91 http://www.slabbe.org/

updated 5 years ago

Indeed, this is not Python syntax, it is SageMath syntax only. Sage preparses this notation and turns it into Python code:

sage: preparse('R.<w> = PolynomialRing(QQ)')
"R = PolynomialRing(QQ, names=('w',)); (w,) = R._first_ngens(1)"

Other examples include:

sage: preparse('2/3')
'Integer(2)/Integer(3)'
sage: preparse('2./3')
"RealNumber('2.')/Integer(3)"
sage: preparse('x^x')
'x**x'

Also, this turns off/on the preparser:

sage: preparser(False)
sage: preparser(True)

link

Comments

Note that this does not exactly answers the question which started with "Are there some documentation ..."

vdelecroix ( 5 years ago )

The relevant documentation is for the function preparse_generators: http://doc.sagemath.org/html/en/refer.... There are more examples (labeled as "TESTS") which are in the code but not the reference manual.

John Palmieri ( 5 years ago )

Some documentation on that syntax can also be found in the section on A Guided tour on Polynomial of the Tutorial of SageMath at http://doc.sagemath.org/html/en/tutor... But it is true that some clearer documentation on this syntax could be explained on its own chapter somewhere.

Sébastien ( 5 years ago )

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