IsHandle

IsHandle(X, local)

IsHandle(X) tests whether the value in «X» is a handle. When «X» is array-valued, it tests whether each cell of the array contains a handle.

IsHandle(X, local: true) tests whether a local variable «X» contains a handle. This form doesn't resolve «X» to its value, and really the only way to tell whether a local variable is acting as an alias of another object. When «X» is something other than the name of a local variable, the optional «local» parameter has no effect.

Library

Special

Examples

For the examples, assume these global variables are defined as follows:

Index I := [1, 2, 3, 4]

Variable hI := Handle(I)

Variable B := Table(I)(0, Null, hI, Handle(hI))

IsHandle(I) → [0, 0, 0, 0] { Indexed by I }

IsHandle(hI) → 1

IsHandle(B) → [0, 0, 1, 1] { Indexed by I; local: true has no effect when «X» is not a local variable }

IsHandle(I, local: true) → [0, 0, 0, 0] { Indexed by I }

IsHandle(hI, local: true) → 1

IsHandle(B, local: true) → [0, 0, 1, 1] { Indexed by I }

Var x := I Do IsHandle(x) → [0, 0, 0, 0] { Indexed by I }

Var x := I Do IsHandle(x, local: true) → 0

Var x := Handle(I) Do IsHandle(x) → [0, 0, 0, 0] { Indexed by I }

Var x := Handle(I) Do IsHandle(x, local: true) → 1

Var x := hI Do IsHandle(x) → [0, 0, 0, 0] { Indexed by I }

Var x := hI Do IsHandle(x, local: true) → 1

Var x := B Do IsHandle(x) → [0, 0, 1, 1] { Indexed by I }

Var x := B Do IsHandle(x, local: true) → 0

LocalAlias x := I Do IsHandle(x) → [0, 0, 0, 0] { Indexed by I }

LocalAlias x := I Do IsHandle(x, local: true) → 0

LocalAlias x := Handle(I) Do IsHandle(x) → [0, 0, 0, 0] { Indexed by I }

LocalAlias x := Handle(I) Do IsHandle(x, local: true) → 1

LocalAlias x := hI Do IsHandle(x) → [0, 0, 0, 0] { Indexed by I }

LocalAlias x := hI Do IsHandle(x, local: true) → 1

LocalAlias x := B Do IsHandle(x) → [0, 0, 1, 1] { Indexed by I }

LocalAlias x := B Do IsHandle(x, local: true) → 0

MetaVar x := I Do IsHandle(x) → [0, 0, 0, 0] { Indexed by I }

MetaVar x := I Do IsHandle(x, local: true) → 0

MetaVar x := Handle(I) Do IsHandle(x) → 1

MetaVar x := Handle(I) Do IsHandle(x, local: true) → 1

MetaVar x := hI Do IsHandle(x) → 1

MetaVar x := hI Do IsHandle(x, local: true) → 1

MetaVar x := B Do IsHandle(x) → [0, 0, 1, 1] { Indexed by I }

MetaVar x := B Do IsHandle(x, local: true) → 0

Index J := 1..5 Do IsHandle(J) → [0, 0, 0, 0, 0] { Indexed by J }

Index J := 1..5 Do IsHandle(J, local: true) → 1

MetaIndex J := [0, Null, hI, Handle(I)] Do IsHandle(J) → [0, 0, 1, 1] { Indexed by J }

MetaIndex J := [0, Null, hI, Handle(I)] Do IsHandle(J, local: true) → 1

Function F(X: Variable) := IsHandle(X, local: true) → 1 { always }

Function F(X: Object) := IsHandle(X, local: true) → 1 { always }

See Also

• Data Type Functions
• Var..Do
• MetaVar..Do
• LocalAlias..Do
• Handle Functions