This is a good opportunity to use case syntax. You can also case on tuples, like this:

```

foo a b = case (a,b) of

(A1,B1) -> fun1

(A1,B2) -> fun2

(A1,B3) -> fun3

(A1,_) -> fun4 <- this is probably not necessary anymore, unless you expect Rule2 to get more constructors.

(A2,B1) -> fun5

...

```

On Thu, May 16, 2019 at 10:14 PM Magicloud Magiclouds <magicloud.magiclouds@gmail.com> wrote:

Hi,
I have trouble describing this clearly. Let me show code directly.

data Rule1 = A1 | A2 | A3
data Rule2 = B1 | B2 | B3

foo a b =
if a == A1
then if b == B1
then fun1
else if b == B2
then fun2
else if b == B3
then fun3
else fun4
...

Basically, Rule1 and Rule2 compose a matrix, for each case of Rule1
and Rule2, I need to do different things. Above is already long and
not quite clear, and it is far from complete.

So my question is, is there a way/lib that I can make this clear to
read/understand?
_______________________________________________
Haskell-Cafe mailing list
To (un)subscribe, modify options or view archives go to:
http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
Only members subscribed via the mailman list are allowed to post.