Isa

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isa (operator)

isa is a keyword binary operator which tests the left-hand operator for membership in the type defined by the right-hand side. That right-hand operand could be a user-defined map (to which the left-hand side might belong via the __isa chain), or it could be one of the built-in types: number, string, list, map, or funcRef.

Examples for built-in types

"Hello" isa string    // returns 1
"Hello" isa number    // returns 0
123 isa number        // returns 1
"123" isa number      // returns 0 
[1,2,3] isa list      // returns 1
{"uno":1,"dos":2} isa map    // returns 1
@print isa funcRef    // returns 1

Examples for user-defined types

MyDefinedType = {}
MyOtherDefinedType = {}

obj = new MyDefinedType

obj isa MyDefinedType        // returns 1 - direct type
obj isa map                  // returns 1 - related by inheritance

obj isa MyOtherDefinedType   // returns 0 - because unrelated

Other types as RHS

As of MiniScript version 1.6.1, it's possible to use any value as a right hand side of an isa operator. When such values are not types, the operator returns false, except when it's a null in which case isa checks for equality with null (this behavior might currently be affected by a bug).

__isa (map entry)

__isa is a special entry in a map that refers to the map's base class. It is part of MiniScript's support for object-oriented programming.

See also

• Object-oriented programming in miniscript
• The map type

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