Re: List: forEach: arg1;

[Ken Cline]

On Wed, 5 Mar 1997, Kevin Crowston wrote:

> "Ludo Pagie" <address@hidden> wrote:
> 
> >-addConcentration: (double) c;
> 
> >[metabList forEach: M(addConcentration:) : myarg];
> >with:
> >
> >>reaction.m: In function `_i_Reaction__react_':
> >>reaction.m:38: incompatible type for argument 4 of indirect function call
> 
> It helps to know that a message send is basically syntactic sugar for a
> function call--the line above is (more or less) turned into the function
> call:
> 
> _i_Reaction__react_(metabList, sel, M(addConcentration), myarg)
> 
> So argument four is myarg.
> 
> >without this line the program compiles (and runs) fine. I guess that the
> >argument 4 is an argument of one of those (?) run-time function-calls (eg.
> >"objc_msgSend" in Next Objective C, don't know about Swarms run-time system).
> 
> The incompatible type comes because the forEach:: expects to get id's as
> arguments, and you're passing a double.  I had similar problems in my
> simulation.  What I ended up doing was: (1) switching to float's, since
> they're the same size as id's, at least on a Sun--you might want to verify
> this on whatever you're using.  (2) passing the float as an id--this was a
> bit ugly, since it turns out you can't simply cast a float to a pointer.
> What I ended up doing was taking a pointer to my float, casting it to a
> pointer to an id, and deferencing the pointer... ugly at best.  If I
> remember correctly, it looked like:
> 
>            (*((id*)(&f)))
> 
> There's probably a more elegant way, but I think this worked.
> 
> Kevin
> 

Of course you could abandon the "forEach" method:

-react: (ChemicalModelSwarm*) chemicals{
  id metabList; // this is a List
  id metabListIndex;  // this is a List Index
  id metabListMember;
  double myarg;
 
  myarg=[uniformDblRand getDoubleWithMin: 0.0 withMax: 1.0];
  metabList=[chemicals getMetaboliteList];

  // I'm not sure whether you wanted to "addConcentration"
  // to the first one twice ??
  [ [metabList getFirst] addConcentration:myarg];

  metabListIndex = [metabList begin: [self getZone] ];
  while ( metabListMember = [metabListIndex next] ) {
     [ metabListMember print ];
     [ metabListMember addConcentration: myarg ];
  }
  [metabListIndex drop];
 
  return self;
}

Just another option...

Ken. 


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Ken Cline                             address@hidden
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