assigned - Maple Help
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assigned

check if a name is assigned

 

Calling Sequence

Parameters

Description

Thread Safety

Examples

Compatibility

Calling Sequence

assigned(n)

assigned(n, val)

Parameters

n

-

name, subscripted name, or function call

val

-

name, assignable

Description

• 

The assigned function returns true if n has a value other than its own name, and returns false otherwise.

  

Note: The assigned function returns true if you have placed assumptions on n using the assume command.

• 

This function is one of the exceptions to the normal evaluation rule for arguments of a function. The argument to assigned will only be evaluated as a name (see the evaln function) rather than fully evaluated.

• 

The definition of assigned for array/table subscripts is

• 

The definition of assigned for function calls is

• 

If an optional second argument is provided, then that parameter is set to the assigned value of n.  This allows the assignment-check and fetch of the value to be done in a single command, which can be important in threaded applications with shared data, and when using weak tables.

Thread Safety

• 

The assigned command is thread-safe as of Maple 15.

• 

For more information on thread safety, see index/threadsafe.

Examples

(1)

(2)

(3)

(4)

Table lookups can return unevaluated; using assigned or comparing against evaln of the indexed name will distinguish between a unevaluated lookup and a found value.

(5)

(6)

(7)

(8)

(9)

(10)

(11)

assigned will evaluate the function to determine if it will return itself or not

f := proc(x) `if`(x::integer,x^2,'procname'(x)) end:

(12)

(13)

(14)

If you place an assumption on a name using the assume command, the assigned command returns true for that name.

(15)

(16)

Note: Evaluating an assigned call under an assumption (using the assuming command), returns true for a name only if it has a value different from its name.

(17)

Compatibility

• 

The assigned command was updated in Maple 2019.

• 

The val option was introduced in Maple 2019.

• 

For more information on Maple 2019 changes, see Updates in Maple 2019.

See Also

anames

assume

assuming

evaln

hasindex

unames

 


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