Function
A QL Expression, that you can use from other expressions
Functions are basically how you do serious programming in Querki. They are, therefore,
very advanced, and are not recommended for anyone aside from programmers.
Technically, a Function is simply an "inside-out" Large Text Property, containing the stuff that
would normally go inside square brackets -- a single QL expression of arbitrary complexity. It is
not often strictly necessary to pull code out into a Function, but is occasionally the only way to
deal with a complex problem such as recursion, and is often helpful for factoring a complex expression.
Note that QL and QText can contain each other, to a nearly arbitrary level of recursion. Just as a Text
Property can contain QL expressions in double-square-brackets, a Function can contain QText in
double-double-quotes.
When a Function is invoked from a QL expression, it receives the passed-in context (the value on the
left-hand side of the "->"), and that will be received by the first stage of this Function. The received
context can also be accessed from anywhere in the Function, as $_context. If the Function is called with
parameters in parentheses, those can be used as $_1, $_2, etc.
Functions are still pretty new, and it is not clear that all of the kinks have been ironed out yet.
If you encounter behaviour that seems to be wrong, please ask about it, and feel free to log an Issue
if you find a bug.
In the future, Functions will be greatly enhanced. Among other things, we plan to add:
- Named parameters
- The ability to declare a Function Signature, specifying the legal Types for the context and params
- The ability to specify the return Type of the Function
- Name bindings for values (basically, the immutable version of variables)
- Mechanisms for changing the Space programmatically
- Type inference, which will attempt to automatically detect the signature and return Type
That is all down the road, however -- for now, a Function is simply a raw block of code, with no
type checking, so use them with care. If you need specific language features, please ask.
Properties that are based on Function
