[Haskell-cafe] Purely Functional Data Structures

[Richard O'Keefe]

On 8 Mar 2009, at 12:13 pm, G?uenther Schmidt wrote:

> Hi Don,
>
> damn, that was quick!
>
> And thx, I'll look into that. The reading it in wasn't much of a  
> problem, I had been able to use MS-ODBC for that, there's a driver  
> for ODBC files. The problem is more the type of data structure I'd  
> be reading it into. In SQL I would have the data indexed by several  
> different columns, if I use maps I'd only have one key, so if I need  
> to lookup data in the map by a value that is not the key the lookups  
> will become quite expensive.
>
> Any suggestions, what do you do in these cases?

Who said you could only have one map?
You can have as many as you want:

	primary :: Map Key1 (Maybe Whole_Record)
	secondary :: Map Key2 [Whole_Record]
	...

Adding the same record to both maps won't copy the record.