Expression Equality Bracket
Overview
The expression equality brackets are given by {= =}. When found inside the body of a dynamic text document, the
expression between the brackets is evaulated and then the brackets are replaced by the value of the expression.
A First Example
The simplest way to understand the exression equality bracket is to see it used in an example. The following
shows placing an expression (in this case, 2+3) inside the brackets.
The sum and 2 and 3 is {= 2+3 =}
Try it!
The generated output in your document will be
Expressions are demarcated with the curly brace and equal sign, which essentially means the text here should equal the value of evaluating the expression
within. If the expression resolves to undefined, nothing is displayed. If it resolves to a promise, then the result will be the result of the promise.
(see
asynchronous programming)
Binding to Data
One of the typical uses of dynamic text is to use outside data to populate the text. For example, suppose that the
prices of a given equity has been imported into your workspace. (data consists of objects such as {date:'2020-01-01', price:100}).
One may wish to quote the maximum price that was attained in the given period.
The maximum price is {= $list($val('prices')).map(p=>p.price).max() =}
The expression does several things. First it retrieves the named dataset "prices" from
$val. Next it wraps it with a $list object.
Using the query mechanism of the
$list api,
the prices are extracted from the list of objects, and then the
maximum value is calculated.
Linking Files
One way to create automation is to have a template of boilerplate text that you want to link into your document.
For example, the boilerplate text that is hosted in the
davinci latex library.
To link in a text file that is hosted at a given URL, you can use the $url function, which retrieves the text.
{= $url('http://www.server.com/boilerplate.txt') =}
For more information about linking and rendering boilerplate templates, see:
boilerplate
