On Jul 8, 2011, at 8:15 PM, Yawar Amin wrote: > Folks, > > On 2011-07-08, at 01:15, Yawar Amin wrote: > >> […] >> I like the idea of XML -> HTML + CSS + JavaScript plots. How about moving to >> a completely declarative XML report, where we use XML tags to ask for things >> like account names and balances, and using the Scheme (or […] > > I got to thinking that Scheme itself can be used as a declarative,* > domain-specific language for defining GnuCash reports. We could have a > declarative API that sits on top of the currently-existing report API, and > abstracts away the complexities of writing out an HTML page and building a > report options dialog box. Sort of like LaTeX hides the raw TeX complexities > of laying out a page. Here’s my income statement converted over from XML into > (declarative) Scheme: > > (report "income-statement" > (defs > (def-date "start-date" "General/Start date" "2011-01-01") > (def-date "end-date" "General/End date" "2011-07-31") > > (def-label "title" "General/Report title" "Income Statement") > (def-label "subtitle" "General/Report subtitle" > '((string (date "start-date")) > "to" > (string (date "end-date")))) > > (def-account-group "income" "Accounts/Income accounts" > '(3288757aa761c7bba993766bfb433466 > e49c976843a1dba40570ed6295e89a33)) > (def-account-group "expenses" "Accounts/Expense accounts" > '(df72fb29f46e90e12c2ba10d582a6148 > e518845492b7b9cfa614cc405a8cf715)) > (def-account "net-profit-loss" "" > "Net Profit (Loss)" > (subtract > (balance (account-group "income")) > (balance (account-group "expenses"))))) > > (title (label "title")) > (subtitle (label "subtitle")) > > (filter-date (date "start-date") (date "end-date”) > (group-date 'month > (tabular > (account-group "income") > (account-group "expenses") > (account "net-profit-loss"))))) > > And here’s the report structure in plain language: > > report > definitions (can double as options for the report options dialog box) > definition of date (start date) > definition of date (end date) > definition of label (report title) > definition of label (report subtitle) > definition of account group (income) > definition of account group (expenses) > definition of a calculated account (net profit or loss = income - expenses) > report title > report subtitle > filter by date (only include transactions within date range) > group by date (monthly–this should show balances in the table as one column > per month) > tabular display (we could also provide a graphical display–i.e. column > chart) > account group (income) > account group (expenses) > account (net profit or loss) > > What I’m trying to express here is that a tabular layout should know how to > display accounts and groups of accounts: put the account name on the left and > the balance on the right. And that the report engine should know how to > re-use the definitions of account groups, labels, and dates to build up the > options dialog box. We can help it along a little, e.g. in the call to > (def-date "start-date" "General/Start date" "2011-01-01") you see that the > second argument is a string that provides the tab the widget should be placed > in (“General”) and widget’s label for the dialog box (“Start date”), > separated by a slash. Oh, and since it’s a def-date, the option widget should > be a date picker. This functionality can all be behind the scenes, leaving > the report developer to just declare what his/her report should contain. > > Note that in the call to (def-account "net-profit-loss" "" Net Profit (Loss)" > …) the second argument is an empty string, meaning don’t place this as a > widget in the options dialog box. > > If we stick with Scheme, we can take advantage of all the low-level functions > that already exist for data extraction and report layout. But we can also > move to a declarative model where we can have convention (re-use the report > definitions as options) over configuration (build an options dialog box). > > Also, is it still true that we have to restart GnuCash every time we change a > Scheme report, to see the changes? In any case, we need to make it dead easy > for users to import and run and custom reports. > > Best, > > Yawar > > * I find that I’m saying ‘declarative’ a lot nowadays–I think it has to do > with the fact that I’m learning Haskell :-) >
Fun. Two questions: Can that be easily converted into a string parser so that normal users aren't put off by the extra parentheses, and is there anything about that that works in Scheme but not in C? Regards, John Ralls _______________________________________________ gnucash-devel mailing list gnucash-devel@gnucash.org https://lists.gnucash.org/mailman/listinfo/gnucash-devel
