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Adds a value to the end of a list and returns the list. If the list provided is empty (that is, list is the empty list [ ], or the value _NULL ), the list returned will contain a single value: [value].
Syntax
addElement(list, value)
| Argument | Type | Description |
|---|---|---|
| list | Any | The list to which value should be added. If this argument is a variable which evaluates to null then a new list will be returned containing only value. If this argument is not a list but a single value then a new list will be returned containing this argument and value. |
| value | Any | The item that should be added to list |
Examples
addElement([ ], 4)Adds 4 as a new entry in an empty list, and returns the result: [ 4 ].
addElement($list, $value)
Adds $value as a new entry at the end of $list, and returns the list. If the list provided is empty (that is $list is the value _NULL ), the list returned will contain a single value $value.
Often it is helpful to iterate over an existing list in order to build a new list, as in the following example:
forEach($name, in.name, if ($name != _NULL, addElement($usableNames, $name) ) )
Using the forEach function we go through every name provided in the variable in.name. We want to get a list of all the names which are not null, so for each one we test the value using the condition $name != _NULL. If the name is not null, we add it to a list called $usableNames using addElement().
ifNull(in.rate, addElement($errors,"Missing rate value"))
If in.rate is not found then an error message is added to a list of errors found so far. This An If() condition is a useful way of building up a list of problems which are found as a stream is processed, which can then be formatted into a list of errors recorded on a Stream Stream is processed.
listToString() can be used to format a list (of errors, say) into a string that can be recorded in a string-valued field on a stream record. Given a list like:
$errors = ["Bad input", "Missing rate value"],
the expression
listToString($errors, "\n") and listToString($errors, ", ") will generate output strings like:
"Bad input
Missing rate value"
and
"Bad input, Missing rate value"
respectively.