Can somebody give me a hint where this kind of syntax
S.<x> = NumberField(x^2-5)
is defined? I mean the S.<x>. It's (relatively) clear from the examples what it does, but I've never seen an a real explanation in the manual.
Thank you.
Hi,
The syntax S.<x>=..., which is not standard Python, is actually interpreted by the Sage preparser. You can find how it is transformed to standard Python by means of the preparse command, with "S.<x>=..." as an argument (don't forget the quotes):
preparse("S.<x> = NumberField(x^2-5)")
The output is
"S = NumberField(x**Integer(2)-Integer(5), names=('x',)); (x,) = S._first_ngens(1)"
As you can see, it is a short-cut ("syntactic sugar") for combining two definitions into a single instruction: the definition of S and that of x, as a generator of S.
This is documented in Sage reference manual: look for sage.repl.preparse.preparse_generators in this page
Asked: 2015-04-28 09:52:04 +0200
Seen: 505 times
Last updated: Apr 28 '15
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