Type checking (class, isa) in MATLAB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the class function do in MATLAB?

The <code>class</code> function returns the type (class name) of a variable as a string, such as 'double', 'char', or a user-defined class name.

beginner

How does the isa function differ from class in MATLAB?

<code>isa</code> checks if a variable is of a specified class or inherits from it, returning true or false. <code>class</code> returns the exact class name as a string.

beginner

What will isa(x, 'double') return if x is a 3x3 matrix of doubles?

It will return true because x is of class 'double'.

intermediate

If obj is an object of a subclass, what does isa(obj, 'SuperclassName') return?

It returns true if obj inherits from SuperclassName, even if obj is not exactly of that class.

beginner

What is the output of class(42) in MATLAB?

The output is 'double' because numeric literals like 42 are stored as double precision by default.

What does class(x) return in MATLAB?

A The class name of x as a string

B True if x is a double

C The size of x

D The value of x

class returns the class name of the variable as a string.

Which function checks if a variable belongs to a class or its subclass?

A class

B isa

C size

D typeof

isa returns true if the variable is of the specified class or inherits from it.

What will isa('hello', 'char') return?

A false

B char

C true

D error

A string like 'hello' is of class 'char', so isa returns true.

If obj is exactly class 'MyClass', what does class(obj) return?

A false

B true

C obj

D 'MyClass'

class returns the exact class name as a string.

Which is true about isa(x, 'double') when x is a double array?

A Returns true

B Returns false

C Returns the size of x

D Returns the class name

isa returns true if x is of class 'double'.

Explain how to check the type of a variable in MATLAB using class and isa.

Think about when you want the exact type name versus when you want to check if it belongs to a class or subclass.

Describe a situation where isa is more useful than class.

Consider object-oriented programming with subclasses.