The evaln function is used to "evaluate to a name" or, more generally, to form an assignable object. The name (assignable object) will not itself be evaluated.

A typical example of its use would be divide(a,b,evaln(t[i])) where i is the index of a for loop.

If the expression is a simple name (i.e. a symbol) then the same effect can be achieved by using single quotes on the name.

evaln can be used on names, subscripts, function calls, and concatenations.

There is also a procedure parameter modifier, evaln, which declares that an argument to a procedure invocation must evaluate to a name.

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

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

$i≔1$

$i≔1$

$\mathrm{evaln}\left(i\right)$

$i$

$\mathrm{evaln}\left(a\Vert i\right)$

$\mathrm{a1}$

$\mathrm{evaln}\left(a\Vert \left(1..3\right)\right)$

$\mathrm{a1},\mathrm{a2},\mathrm{a3}$

$\mathrm{evaln}\left(t\left[i\right]\right)$

$t_1$

$\mathrm{evaln}\left(f\left(i\right)\right)$

$f\left(1\right)$

$\mathrm{divide}\left(x^2\,x\,\mathrm{evaln}\left(t\left[i\right]\right)\right)$

$\mathrm{true}$

$t\left[i\right]$

$x$

$\mathrm{evaln}\left(3\right)$

Error, illegal use of an object as a name