mustBeLessThan

Validate that value is less than another value

Syntax

mustBeLessThan(value,c)

Description

mustBeLessThan(value,c) throws an error if any elements in value are greater than or equal to c. This function does not return a value.

mustBeLessThan calls the lt function to determine if value is less than c. (since R2026a)

Class support: All numeric classes, logical, and MATLAB^® classes that implement lt.

This function ignores empty values in the first input argument. Therefore, no error is thrown when the property or function argument value is empty.

Examples

Validate First Input Less Than Second

Use mustBeLessThan to validate that the values in the first input are less than the value of the second input.

mustBeLessThan([2 3 4],2)

Value must be less than 2.

Restrict Property Values

Restrict property values to be less than a specified value.

This class constrains the value of Prop1 to be less than 2.

classdef MyClass
   properties
      Prop1 {mustBeLessThan(Prop1,2)}
   end
end

Create an object and assign a value to its property.

obj = MyClass;
obj.Prop1 = 2;

Error setting property 'Prop1' of class 'MyClass'. Value must be less than 2.

When you assign a value to the property, MATLAB calls mustBeLessThan with the value being assigned to the property. mustBeLessThan issues an error because the value 2 is not less than 2.

Restrict Function Argument Values

This function restricts the input argument to be values that are less than 5.

function r = mbLessThan(x)
    arguments
        x {mustBeLessThan(x,5)}
    end
    r = x + 5;
end

Calling the function with a vector that contains values that are greater than or equal to 5 does not meet the requirements defined with mustBeLessThan and results in an error.

x = [1.27, 4.54, 3.9, 5.0, .531];
r = mbLessThan(x);

Error using mbLessThan (line 3)
 r = mbLessThan(x);
                ^
Invalid argument at position 1. Value must be less than 5.

Input Arguments

value — Value to validate

scalar | array

Value to validate, specified as a scalar or an array of one of these types:

• logical, char, string, or numeric class

• MATLAB classes that implement lt

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical | char | string | categorical | datetime | duration | table | timetable
Complex Number Support: Yes

c — Constant value that the value argument must be less than

scalar | array

Constant value that the value argument must be less than, specified as a scalar or an array of one of these types:

• logical, char, string, or numeric class

• MATLAB classes that implement lt

Inputs c and value must have compatible sizes (for example, value is an M-by-N matrix and c is a scalar or 1-by-N row vector). For more information, see Compatible Array Sizes for Basic Operations.

Before R2026a: c must be scalar.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical | char | string | categorical | datetime | duration | table | timetable
Complex Number Support: Yes

Tips

• mustBeLessThan is designed to be used for property and function argument validation.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

GPU Code Generation
Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

GPU Arrays

Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.

The mustBeLessThan function fully supports GPU arrays. To run the function on a GPU, specify the input data as a gpuArray (Parallel Computing Toolbox). For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).

Distributed Arrays

Partition large arrays across the combined memory of your cluster using Parallel Computing Toolbox™.

The mustBeLessThan function fully supports distributed arrays. For more information, see Run MATLAB Functions with Distributed Arrays (Parallel Computing Toolbox).

Version History

Introduced in R2017a

R2026a: mustBeLessThan no longer restricts inputs to be real, numeric, or logical

The mustBeLessThan function no longer calls the isreal, isnumeric, and islogical functions to validate input. As a result, mustBeLessThan accepts any data type supported by the underlying comparison operator lt (or <), such as character vectors, strings, and date and time types.

For example, the compareValues function restricts input argument values using the mustBeLessThan validation function.

function obj = compareValues(startValue,endValue)
    arguments
        startValue
        endValue {mustBeLessThan(startValue,endValue)}
    end
end

The compareValues function now accepts data of type datetime as input.

A = datetime("yesterday");
B = datetime("today");
compareValues(A,B)

In previous releases, calling compareValues with datetime inputs returned this error:

Error using compareValues (line 4)
Inputs to function 'mustBeLessThan' must be numeric or logical.

To preserve the behavior of previous releases, explicitly use mustBeReal and mustBeNumericOrLogical in your validation checks. For example, this code preserves the previous behavior of mustBeLessThan in the compareValues function definition.

function obj = compareValues(startValue,endValue)
    arguments
        startValue {mustBeReal,mustBeNumericOrLogical}
        endValue {mustBeReal,mustBeNumericOrLogical, ...
                  mustBeLessThan(startValue,endValue)}
    end
end

R2026a: Compare two inputs with compatible array sizes

The mustBeLessThan function now supports implicit expansion when comparing two inputs with compatible array sizes, similar to the implicit expansion behavior in arithmetic operations.

For example, the compareValues function restricts input argument values using the mustBeLessThan validation function.

function obj = compareValues(startValue,endValue)
    arguments
        startValue
        endValue {mustBeLessThan(startValue,endValue)}
    end
end

The compareValues function now accepts inputs with compatible array sizes.

compareValues([-2; -1],[3 2 1])

In previous releases, calling compareValues on 2-by-1 and 1-by-3 input arrays returned this error:

Error using compareValues (line 4)
Second input to function 'mustBeLessThan' must be a scalar.