On Wed, Aug 19, 2009 at 2:56 PM, rjf<fate...@gmail.com> wrote: > > Let's see, in sage then you have the following syntax. > (x,y) means a list
Not at all. (x, y) is a tuple. [x, y] is a list. > f(x,y) means a function application > (x+y) means grouping for arithmetic. > RationalField(x) means, uh, sortof "in indeterminate..." > Integer(4) means, uh, set the type? force a coercion? > > Are there any other distinct uses of ()? > > > However, the Sage choice is kind of confusing. > x //a variable > (x ) // a list of one item or a group consisting of x alone, hence x. > ((x)) // a list of one item, grouped alone. Or a list of a list of > one item. Or just x. > > That is, if (a+1,a+2) is a list of 2 items, is (a+1) not a list of > one item? > > I'm sure there is a simple explanation. Yes, the explanation is that you're mixing up ()'s and []'s. You *could* actually try out the above in Sage to see whether you're right or not, instead of making it up: sage: a = 1; a 1 sage: type(a) <type 'sage.rings.integer.Integer'> sage: a = (1); a 1 sage: type(a) <type 'sage.rings.integer.Integer'> sage: a = ((1)); a 1 sage: type(a) <type 'sage.rings.integer.Integer'> sage: a = (((((((1))))))); a 1 So in the absence of a function in front of (), and in the absence of commas inside (), it's what you call "grouping for arithmetic". Now for lists: sage: a = [1]; a [1] sage: type(a) <type 'list'> sage: a[0] 1 sage: type(a[0]) <type 'sage.rings.integer.Integer'> sage: a = [[1]]; a [[1]] sage: type(a) <type 'list'> sage: a[0] [1] sage: type(a[0]) <type 'list'> sage: a[0][0] 1 sage: type(a[0][0]) <type 'sage.rings.integer.Integer'> These seem unambiguous to me. If you're after the tuple with one element 1, a = (1,) does the trick, as Ondrej pointed out. Best, Alex > > > -- Alex Ghitza -- Lecturer in Mathematics -- The University of Melbourne -- Australia -- http://www.ms.unimelb.edu.au/~aghitza/ --~--~---------~--~----~------------~-------~--~----~ To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
