Healix Expression Grammar

Healix includes a programming language like grammar for defining calculations.

This is very similar in concept to formulas in Microsoft Excel or Google Sheets. In these spreadsheets, data is pulled from a matrix, where A1 is the upper left cell of a sheet, and B1 is the cell to A1's right. To add these to cells together you can enter A1 + B1.

In Healix, all the data is in forms or are attributes of a plan. As discussed in Data References, in Healix you can use submission.form1.field1 to reference a field called field1 for a form called form1.

However, a form can be submitted multiple times. So we need a way to identify which submission to use. This is where functions come in. One of the most commonly used functions is lastVal. lastVal tells the expression interpreter that we want the "last value", or the one that was submitted most recently. So

lastVal("submission.form1.field1")

returns the last value of field1 in form1 that was submitted.

Calculation Contexts

When a calculation is executed it has access to certain data, depending on where it is run from.

For example, if a form submission is in context, the fields from the submitted form are in context and do not need to be qualified by the entity and form levels. For example:

submissionVal("field1")

returns the value of "field1", but this only works in contexts where the system knows which form you are referencing. For example, defining a View for a submission.