On Wed, Sep 17, 2008 at 08:37:36PM +0800, Chris Davaz wrote: > I am confused about how we should setup method signatures: > > Let's take a look at a line in any-str.pir: > > 46 .sub 'comb' :method :multi(_) > 47 .param pmc regex > 48 .param int count :optional > 49 .param int has_count :opt_flag > > As you can see we have one parameter specified in :multi which is _ (any > type). However we also have two .param lines, 47 and 48. So here are some > questions: > > I noticed 'self' is implicitly defined, however does 'self' eat up a > parameter? Should we always have one parameter in :multi specified for the > object the method is running on?
Yes, the first argument of the :multi refers to the invocant. > Also, I played around with :multi by putting in different things. With the > above method here is what I tried and the result > > :multi(_) - works Restricts the sub to being invoked by callers supplying at least one argument (in this case, the argument is the invocant, since the sub is declared as :method). > :multi(_, _) works This says that the sub requires at least two arguments (of any type). The first will go into 'self', the second into 'regex'. > :multi(_,_,_) doesn't work This says that the sub requires at least three arguments (of any type). This doesn't really match the sub definition though, which has an invocant, a required argument, and an optional argument. > :multi(_,Integer) doesn't work This says the invocant may be of any type, and the first argument must be an Integer (or a subclass of Integer). Probably not what we want given that the first parameter of the sub is 'regex'. > :mult(Sub) doesn't work This says that the sub can be invoked only on Sub invocants. > Some clarification surrounding the use of :multi would help a lot. Hope the above helps. I don't know where :multi is documented in Parrot itself; the pdd27 file doesn't provide much detail. Pm
