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Delayed evaluation without all the parenthesis?

asked 2011-11-09 21:28:18 -0500

Alister gravatar image

updated 2011-11-10 09:04:02 -0500

Is there a way to have delayed evaluation without having unnecessary parenthesis. For example,

(x.add(x, hold = True)).add(x, hold = True)

gives

(x + x) + x

not

x + x + x

Thanks

EDIT:

Great answer burcin! I was hoping to be able to it in more of a binary way though, so that I could use the Infix hack from http://code.activestate.com/recipes/3....

I wanted to make a binary operator which is still delayed. Defined here

class Infix(object):
    def __init__(self, function):
        self.function = function
    def __ror__(self, other):
        return Infix(lambda x: self.function(other, x))
    def __or__(self, other):
        return self.function(other)

p=Infix(lambda x,y: x.add(y, hold=True))

Usage is

x |p| x |p| x
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2 answers

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answered 2011-11-10 01:12:47 -0500

Is this what you need?

sage: x.add(x,x,hold=True)
x + x + x
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answered 2011-11-10 11:05:50 -0500

Jason Grout gravatar image

Sage already has an infix_operator decorator:

sage: @infix_operator('or')
....: def f(x,y): return x.add(y, hold=True)
....: 
sage: x |f| x |f| x
(x + x) + x

See http://sagemath.org/doc/reference/sag...

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Comments

Nice! But that still leaves some unnecessary parenthesis.

Alister gravatar imageAlister ( 2011-11-10 12:09:30 -0500 )edit

Does your infix operator not have the parentheses? The parentheses are showing exactly what you typed, using order of operations, using a *binary* addition operator.

Jason Grout gravatar imageJason Grout ( 2011-11-10 12:49:41 -0500 )edit

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Asked: 2011-11-09 21:28:18 -0500

Seen: 180 times

Last updated: Nov 10 '11