parser/special_parser library

Classes

AggregateParser

Performs general-purpose aggregation by evaluating the aggregator expression for each element of the input collection. Within this expression, the standard iteration variables of $this and $index can be accessed, but also a $total aggregation variable. The value of the $total variable is set to init, or empty ({ }) if no init value is supplied, and is set to the result of the aggregator expression after every iteration. Using this function, sum can be expressed as: value.aggregate($this + $total, 0) Min can be expressed as: value.aggregate(iif($total.empty(), $this, iif($this < $total, $this, $total))) and average would be expressed as: value.aggregate($total + $this, 0) / value.count()

BracketsIndexParser

DotParser

EmptySetParser

There is no literal representation for null in FHIRPath. This means that when, in an underlying data object (i.e. they physical data on which the implementation is operating) a member is null or missing, there will simply be no corresponding node for that member in the tree, e.g. Patient.name will return an empty collection (not null) if there are no name elements in the instance. In expressions, the empty collection is represented as { }.

IndexParser

If the function takes an expression as a parameter, the function will evaluate the expression passed for the parameter with respect to each of the items in the input collection. These expressions may refer to the special $this and $index elements, which represent the item from the input collection currently under evaluation, and its index in the collection, respectively. For example, in name.given.where($this > 'ba' and $this < 'bc') the where() function will iterate over each item in the input collection (elements named given) and $this will be set to each item when the expression passed to where() is evaluated.

IterationContext

ThisParser

If the function takes an expression as a parameter, the function will evaluate the expression passed for the parameter with respect to each of the items in the input collection. These expressions may refer to the special $this and $index elements, which represent the item from the input collection currently under evaluation, and its index in the collection, respectively. For example, in name.given.where($this > 'ba' and $this < 'bc') the where() function will iterate over each item in the input collection (elements named given) and $this will be set to each item when the expression passed to where() is evaluated.

TotalParser