less than (<)

Block Category: Boolean

Inputs: Real, complex, or fixed-point scalars, or vectors or matrices.

On the input connector tabs, “l” represents the x1 and “r” represents the x2.

Description: The < block produces an output signal of 1 if and only if input signal x1 is less than input signal x2. Otherwise, the output is 0. On the connector tabs, “l” represents x1 and “r” represents x2.

Right-click the < block to assign a different function to the block.



1. Simple if-then-else construct

Consider a variable y such that:

If t < 4 then y = 1; else y = 0

Assume that t is simulation time realized as:


By multiplying a constant value 1 with the output of the < block, y is guaranteed to assume a value of 0 until the inequality is true. When the inequality is true, y assumes a value equal to the output of the * block.

2. Modified if-then-else construct

The previous example can also be realized as:


The key difference in implementation is the use of a merge block rather than a * block. The merge block explicitly depicts the if-then-else structure; the * block is a shortcut and can lead to confusion.