Hi Martin,
without looking into topology.spad I guess the reason for you problem
comes from the line
h : Homset(source,target) := homset()
The interpreter remembers now the type of h. And this cannot change in a
session unless you say
)clear prop h
)co fricas/topology.spad
source := topoSpaceFiniteLeftOrder(["a","b","c"])
target := topoSpaceFiniteLeftOrder(["d","e"])
h : Homset(source,target) := homset()
)co fricas/topology.spad
source := topoSpaceFiniteLeftOrder(["a","b","c"])
target := topoSpaceFiniteLeftOrder(["d","e"])
h : Homset(source,target) := homset()
You declare a new variable "source" (no, it is not the same as in the
first definition/assignment). Well, it's the same variable, but it value
changed in the sense that it now points to a different memory location.
Then you use it in "h : Homset(source,target) := homset()". Fine,
but after the second "source := ...", "Homset(source,target)" and the
one you used before are "two different types".
FriCAS ensures that, for example Polynomial(Integer) and
Polynomial(Integer) are the same types, but not that Foo(v1) is the same
as Foo(v2) even if v1 and v2 represent the same value (that is NOT a
domain or category).
Maybe I am wrong, but I have seen such errors
You cannot declare h to be of type Homset([[a,b,c],CONCAT(topology=,
[BRACE(1),BRACE(1,2),BRACE(1,2,3)])],[[d,e],CONCAT(topology=,[
BRACE(1),BRACE(1,2)])]) because either the declared type of h or
the type of the value of h is different from Homset([[a,b,c],
CONCAT(topology=,[BRACE(1),BRACE(1,2),BRACE(1,2,3)])],[[d,e],
CONCAT(topology=,[BRACE(1),BRACE(1,2)])]) .
several times.
The way around this is that you do not declare h to be of a certain
type, but rather put the type onto the right-hand side.
I guess
h := homset() $ Homset(source,target)
should do the trick. (I haven't actually tested it locally.)
Ralf
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