Tim:
Interesting. Is there a similar function that is more
structural? say, can I test whether some domain (which may
be passed as a parameter of type Field) is of the form
Fraction(something) and if so, extract "something" (that
is, assign it to a variable and further test it), sort of
a deconstruction?
William
On Mon, 09 Nov 2009 19:51:45 -0500
Tim Daly <[email protected]> wrote:
You can get a memory pointer to a lisp object.
a:=Fraction(Integer)
returns the "memory location of Fraction(Integer)"
You can prove this with
b:=Fraction(Integer)
EQ(a,b)$Lisp
The lisp function EQ compares memory pointers.
There is a lisp function to get the hash value of any
object
call sxhash. You can call it.
SXHASH(a)$Lisp
Note that if
c:=Integer
then
EQ(a,c)$Lisp is false
SXHASH(a)$Lisp is not equal to SXHASH(c)$Lisp
Thus the hash function you seek already exists.
You just have to accept the fact that Spad is only
syntactic
sugar for lisp code and lisp is not evil.
Tim
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William Sit, Professor Emeritus
Mathematics, City College of New York
Office: R6/202C Tel: 212-650-5179
Home Page: http://scisun.sci.ccny.cuny.edu/~wyscc/
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