This makes it possible to internationalize strings while still using
I/O streams. For example:
std::cout << ACCUM(_("Hello to %1 and %2!") << "me" << "you")
<< std::endl;
The purpose of this class is much like Emacs' (interactive) form: it
allows a value expression function to declare exactly how many
arguments, and of what type, it intends to receive. It then offers
type-safe access to theese arguments in a consistent manner.
An example value expression function definition in C++:
value_t fn_foo(call_scope_t& scope) {
// We expect a string, an integer, and an optional date
interactive_t args(scope, "sl&d");
std::cout << "String = " << args.get<string>(0)
<< "Integer = " << args.get<long>(1) << std::endl;
if (args.has(2)) // was a date provided?
std::cout << "Date = " << args.get<date_t>(2) << std::endl;
return NULL_VALUE;
}
There is also an in_context_t<T> template, which finds the context type
T in the current scope hierarchy. The in_context_t then also acts as a
smart pointer to reference this context object, in addition to serving
the same duty as interactive_t. This combination of intent is solely
for the sake of brevity.
value_t fn_bar(call_scope_t& scope) {
in_context_t<account_t> env(scope, "sl&d");
std::cout << "Account name = " << env->fullname()
<< "String arg = " << env.get<string>(0)
<< std::endl;
return NULL_VALUE;
}
As you can see here, 'env' acts as a smart pointer to the required
context, and an object to extract the typed arguments.
The purpose of this option is that usually when you do a --monthly
periodic report, you see dates ranges from the first day of each month,
to the last day. With --exact, the first day of each range will be the
date of the first transaction found in that range, and likewise with the
end of the range. Essentially it "contracts" the reported period dates
to reflect the exact begin and end dates.
