Random

Introduction

The C++ Standard Library provides functions to generate pseudo-random numbers. These can be used in VEXcode IQ for behaviors that require variability or chance.

Functions

The <cstdlib> library includes the following functions:

• rand — Returns a random integer.

• srand — Sets the random seed.

rand

Returns a random integer between 0 and 2,147,483,647.

Available Functions

int rand();

Parameters

This function does not accept any parameters.

Return Values

Returns a random integer between 0 and 32767.

Notes

• To return a random integer within an exclusive limit, use the pattern rand() % max.

• To return a random integer within a specific range, use the pattern rand() % (max - min + 1) + min.

Examples

// Display a random number
Brain.Screen.print("%d", rand());

// Display a random number between 0 and 100
Brain.Screen.print("%d", rand() % 101);

// Display a random number between 5 and 10
Brain.Screen.print("%d", rand() % (10 - 5 + 1) + 5);

srand

Sets the seed to be used by the pseudo-random number generator in the rand function.

Available Functions

void srand( unsigned int seed );

Parameters

Parameter	Type	Description
seed	unsigned int	The starting seed value.

Return Values

This function does not return a value.

Notes

• Call srand only once, near the start of your project, before calling rand. You do not need to call it before every rand.

• If srand is never called, the program behaves as if srand(1) was used. This means rand produces the same sequence of numbers every time the project runs.

• To get different results each time the project runs, seed with a value that changes between runs, such as the Brain’s timer.

• To get the same results every time (useful for testing), seed with a fixed number such as srand(1).

Examples

// Use the same seed for random number
srand(5);
Brain.Screen.print("%d", rand() % 100);