Before Variables: 3. Oversimplified Parameters — The Control Room 🟢

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$$ {\Large\text{A variable is a named place where Vex temporarily keeps a value.}} $$

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TL:DR

Fundamentals

Variables let us name information, reuse it, and change it easily.

float speed = 5.0;

Create a variable called speed and put 5.0 in it.

Then you can use that value:

@P.y += speed;

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An important distinction

This creates a VEX variable.

float speed = 5.0;

This creates an attribute called speed.

f@speed = 5.0;

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$$ {\Large\begin{array}{c}\text{VARIABLE} \quad \text{temporary information used while your VEX code is running.}\\[8pt]\text{ATTRIBUTE} \quad \text{data stored as part of the geometry.}\end{array}} $$

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Why do we need variables?

Variables give values a name so we can refer to, reuse, and change them easily.

3 Things to Know About Variables

1. Variables can be changed

The name speed still refers to the same variable, but its value has changed.

float speed = 5.0;
speed = 10.0;

2. A variable has a type

A variable has a type that describes what kind of value it stores.

float speed = 5.0;
vector direction = {0,1,0};
int count = 10;

3. Variables are temporary

VARIABLE — A temporary piece of information used while your VEX code is running.

ATTRIBUTE — Data stored on the geometry and available to other nodes.

Types of Variables

The type tells VEX what kind of value it can hold.

The same type can be used for a variable or stored as a geometry attribute.

In Vex

// Create an integer variable from the "a" parameter
int i = chi("a");

// Store the integer as an integer attribute
i@i = i;

// Create a float variable from the "b" parameter
float f = chf("b");

// Store the float as a float attribute
f@f = f;

// Create a vector variable from the "c" parameter
vector v = chv("c");

// Store the vector as a vector attribute
v@v = v;

// Create a string variable from the "d" parameter
string s = chs("d");

// Store the string as a string attribute
s@s = s;

// Create a matrix variable from the "e" parameter
matrix m = ch4("e");

// Store the matrix as a 4×4 matrix attribute
4@m = m;

Operations with Variables

Variables can be used in calculations and expressions.

Arithmetic

In Vex

float speed = 5.0;
float doubled = speed * 2;
float faster = speed + 3;

The same operations work with other numeric types, such as int:

int count = 5;
int doubled = count * 2;
int more = count + 3;