Re: First shot at lisp mini-app - How to make it lispy and not lisp-c



jonathon wrote:

The original app is in Python with GTK as the interface.  It maintains
a list of accounts and their starting balances.  Transactions are saved
in a list in an object called the TransactionManager (TM).

At reconciliation time, each account queries the TM for transactions
referring to said account.  The amount is extracted from the
transaction, and added to (or subtracted from) the balance.  Simple.

First, in Python, when each account object is created, it receives a
reference to the TransactionManager.  In Lisp, should this just be a
global variable that each account object calls when needed, or should
it be stored in a slot within the account object?  What precedent would
there be for this kind of decision?

I am not sure why the object has to know the TM. The code posting transactions should know that. Sounds like you are trying to make account objects self-sufficient for some reason. Anyway, I would have a slot for TM in the Account class only if I planned to have several TMs, to have Account instances accept transactions from only one TM, and if my logic was going to be regularly posting to multiple accounts managed by different TMs. ie, Hard to imagine.

But this is all OO design, not Lisp vs. Python.


Second, what can I look for that would be an indication of too much
like Python or C, where I should try to be more Lisp-ish, such as using
macros, closures, etc?


You should consider writing a macro if you find yourself writing repeated patterns of code (boilerplate) which cannot be functions because they wrap variable chunks of code. Note that a closure containing the variable code could be passed to a function instead of using a macro, so a macro just looks a little cleaner.

kt


--
Cells? Cello? Cells-Gtk?: http://www.common-lisp.net/project/cells/
Why Lisp? http://lisp.tech.coop/RtL%20Highlight%20Film

"Doctor, I wrestled with reality for forty years, and I am happy to state that I finally won out over it." -- Elwood P. Dowd

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