Am 24.04.2012 15:25 schrieb rusi:
Identity, sameness, equality and the verb to be are all about the same
concept(s) and their definitions are *intrinsically* circular; see
http://plato.stanford.edu/entries/identity/#2
Mybe in real life language. In programming and mathematics there are
several forms of equality, where identity (≡) is stronger than equality (=).
Two objects can be equal (=) without being identical (≡), but not the
other way.
As the ≡ is quite hard to type, programming languages tend to use other
operators for this.
E.g., in C, you can have
int a;
int b;
a = 4;
b = 4;
Here a and b are equal, but not identical. One can be changed without
changing the other.
With
int x;
int *a=&x, *b=&x;
*a and *b are identical, as they point to the same location.
*a = 4 results in *b becoming 4 as well.
In Python, you can have the situations described here as well.
You can have a list and bind it to 2 names, or you can take 2 lists and
bind them to that name.
a = [3]
b = [3]
Here a == b is True, while a is b results in False.
Thomas
And the seeming simplicity of the circular definitions hide the actual
complexity of 'to be'
for python: http://docs.python.org/reference/expressions.html#id26
(footnote 7)
for math/philosophy:
http://www.math.harvard.edu/~mazur/preprints/when_is_one.pdf
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