A question about combining constraints

[Mohamed Shafi]

On 12 November 2010 18:39, Joern Rennecke <amylaar@spamcop.net> wrote:
> Quoting Mohamed Shafi <shafitvm@gmail.com>:
>
>> So i have the following questions:
>>
>> 1. Why is that constraints are not matched here?
>
> Please read the node "Register Classes" in doc/tm.texi .
>

I am sorry , could you please highlight the relevant portion for me?
In the pattern that i have given the combination (a,W) satisfies the
pattern. But its not matched because i have given then like (da,Wd). I
know that we can combine the constraints together.

Shafi