Setup Blocks

You might have noticed on previous pages that, every time we defined a <math> or <number> object, the value was displayed on screen. You can avoid that by using the <setup> tag; anything between <setup> and </setup> will be defined and available to use throughout your document, but will not be displayed on screen.

In the following example, the numbers $a$, $b$, and $c$ are defined as <math> objects; then they’re used to compute the discriminant $b^2 - 4 a c$ . None of those definitions and computation are displayed on screen, but all four numbers are used later on.

<setup>  
  <math name="a">2</math>
  <math name="b">8</math>
  <math name="c">6</math>
 
  <math name="discr" simplify>
    $b^2 - 4*$a*$c
  </math>
</setup>
 
<p>Equation: <m><math simplify>
  $a*x^2+$b*x+$c
</math> = 0</m></p>
 
<p>Discriminant: $discr</p>

Test code here.

For comparison, here’s the same code with <setup> and </setup> removed. The four numbers from the <setup> block are all displayed on screen, which is confusing to the user!

<math name="a">2</math>
<math name="b">8</math>
<math name="c">6</math>
 
<math name="discr" simplify>
    $b^2 - 4*$a*$c
</math>
 
<p>Equation: <m><math simplify>
  $a*x^2+$b*x+$c
</math> = 0</m></p>
 
<p>Discriminant: $discr</p>

Test code here.

Throughout the rest of this tutorial, we’ll frequently use <setup> for definitions and computations that don’t need to appear on screen.

Next Steps

It’s time to make our documents interactive! In the next section we’ll learn the basics of how to get user input in a DoenetML document.