The is check can be done in when branch expressions as well. So here, our when has two branches, one for if the object is Frog, plus an else for other cases.

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Abstract Classes Adding Functions to Classes Adding Properties to Classes Chaining to Superclass Functions Checking Inheritance Via is Classes and Instances Constructor Init-Only Parameters Constructors Data Class enum and Functions enum and when() enum Class enum name and ordinal enum valueOf() enum values() Formal Constructor Declaration Hello, World! (In a Class) Inheritance Inheritance and Constructors Inheritance and Functions Inheritance and Overriding Functions Init Block Inner Classes Inner Classes and Outer this Inner Classes and this is and when Manual Casts Nested Classes Nested Classes and Private Access Non-Nested Sealed Classes override is Transitive Overriding Properties Passing this as a Parameter Printing the Class of Numbers Sealed Classes Sealed Classes and when Secondary Constructors Smart Casts The this Pseudo-Property
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