Expression (expression v0.3.1)
Expression is an expression language which consists of the functions provided by Excel with a few additions.
Function and variable names are not case-sensitive so UPPER is equivalent to upper:
contact.name -> Marshawn Lynch FIRST_WORD(contact.name) -> Marshawn first_word(CONTACT.NAME) -> Marshawn
For templating, RapidPro uses the @ character to denote either a single variable substitution
or the beginning of an Expression block.
@ was chosen as it is known how to type by a broad
number of users regardless of keyboard. It does have the disadvantage of being used in
email addresses and Twitter handles, but these are rarely ambiguous and escaping can be
done easily via doubling of the character (
Functions are called by using the block syntax:
10 plus 4 is @(SUM(10, 4))
Within a block,
@ is not required to refer to variable in the context:
A template can contain more than one substitution or block:
Hello @contact.name, you were born in @(YEAR(contact.birthday))