binding Namespace Reference

Contains utility functions for binding expression tree branches. More...

Functions
BindResult	bindMultiple (const QList< PlotInstance * > &curves, PlotBindingTracker &bindTracker, BindInfo &head, BindInfo *tail, unsigned tailLength, bool repeatLast)
	Bind multiple expressions, ensuring exhaustive binding combinations. More...

Detailed Description

Contains utility functions for binding expression tree branches.

Tree based PlotExpression objects may require binding on multiple branches. Each branch may in turn require binding multiple times. For example, consider the following expression:

r'speed.*' - r'speed.*'

This creates the following expression tree:

        PlotSubtract
          /   \
PlotSample    PlotSample

Both PlotSample nodes are using regular expressions. Now, if the available curves are: [ 'speed_measured', 'speed_reported' ], then the resulting bindings should result in a comparison of 'speed_measured' against 'speed_reported'. The bindMultiple() functions handle this sort of exhaustive binding, resulting in four bindings in this case:

• 'speed_measured' - 'speed_measured'
• 'speed_reported' - 'speed_reported'
• 'speed_measured' - 'speed_reported'
• 'speed_reported' - 'speed_measured'

While this is excessive, it ensures all required bindings are made.

The bindMultiple() functions should be used by any PlotExpression which has two or more child expressions. For such an expresison, the bind() method should look somewhat as follows:

 BindResult bind(const QList<PlotInstance *> &curves, PlotBindingTracker &bindTracker, PlotExpressionBindDomain &domain, bool repeatLastBinding)
 {
   if (!_left || !_right)
   {
     return BindError;
   }

   BindInfo bindings[2];
   bindings[0].expression = _left;
   bindings[1].expression = _right;

   repeatLastBinding = repeatLastBinding || bindTracker.isHeld(this);
   BindResult bindResult = binding::bindMultiple(curves, bindTracker, bindings[0], &bindings[1], 1, repeatLastBinding);
   domainUnion(domain, bindings[0].domain, bindings[1].domain);
   return bindResult;
}

This is a binary binding. A ternary binding would have additional elements in bindings.

Function Documentation

BindResult binding::bindMultiple	(	const QList< PlotInstance * > &	curves,
		PlotBindingTracker &	bindTracker,
		BindInfo &	head,
		BindInfo *	tail,
		unsigned	tailLength,
		bool	repeatLast
	)

Bind multiple expressions, ensuring exhaustive binding combinations.

This binds the expression at head, then recurses to bind the remaining items in tail. The overall bind result is a combination of the head and tail results as follows:

Head Result	Tail Result	Final Result
Any	BindError	BindError
Any	BindFailure	BindFailure
BindError	Any	BindError
BindFailure	Any	BindFailure
Bound	Bound	Bound
Bound	BoundMaybeMore	BoundMaybeMore
BoundMaybeMore	Bound	BoundMaybeMore
BoundMaybeMore	BoundMaybeMore	BoundMaybeMore

Parameters

curves	The curves available for binding.
bindTracker	Tracks bind state for later bindings.
head	The head of the list of items to bind.
tail	A list of remaining expression requiring binding.
tailLength	Number of elements in tail.
repeatLast	True to remake the last binding if possible (as defined in bindTracker).

Returns

The overall binding result as described in the table above.