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.

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

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

$n≔4$

$n≔4$

$\mathrm{assigned}\left(n\right)$

$\mathrm{true}$

$\mathrm{assigned}\left(n\,'\mathrm{nval}'\right)$

$\mathrm{true}$

$\mathrm{nval}$

$4$

$a≔\mathrm{table}\left(\mathrm{symmetric}\right)$

$a≔table\left(\mathrm{symmetric}\,\left[\right]\right)$

$a\left[1,2\right]≔x$

$a_{1,2}≔x$

$\mathrm{assigned}\left(a\left[1,2\right]\right)$

$\mathrm{true}$

$\mathrm{assigned}\left(a\left[2,1\right]\right)$

$\mathrm{true}$

$\mathrm{assigned}\left(a\left[1,1\right]\right)$

$\mathrm{false}$

$\mathrm{assigned}\left(\mathrm{abs}\left(x\right)\right)$

$\mathrm{false}$

$\mathrm{assigned}\left(\mathrm{abs}\left(2\right)\right)$

$\mathrm{true}$

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

$\mathrm{assigned}\left(f\right)$

$\mathrm{true}$

$\mathrm{assigned}\left(f\left(x\right)\right)$

$\mathrm{false}$

$\mathrm{assigned}\left(f\left(2\right)\right)$

$\mathrm{true}$

$\mathrm{assigned}\left(b\right)$

$\mathrm{false}$

$\mathrm{assume}\left(b\,\mathrm{positive}\right)$

$\mathrm{assigned}\left(b\right)$

$\mathrm{true}$

$\mathrm{assigned}\left(c\right)\mathbf{assuming}c::\mathrm{integer}$

$\mathrm{false}$

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.