The variable system presented here is actually an artifact to make explicit
which values may change over time and which don't. It also guides the user
to create variables before use them and do so in a more natural way. Somehow,
it tries to be similar to
IORefs, while they aren't. Strictly speaking, they
do not contain any value, but it will contain a value when processing.js executes
the resulting code. To make sure you are doing the right thing, variables are
typed, thus forcing you to feed the correct functions with the correct values.
However, this also leads to weird things like the one described in
Create a new variable with a starting value.
The creation of variables is restricted to the
Read a variable.
Funny fact: it does not matter when you execute this function. The result will always hold the last value asigned to the variable. For example, this code
v <- newVar 10 ten <- readVar v writeVar v 20 point (10,ten)
will draw a point at (10,20).