ASSERT is used to guarantee pre- and post-conditions while a Maple procedure is executing.

If the first argument evaluates to false, an error is generated and the second argument is printed in order to identify the nature of the failure. Such an error cannot be trapped via try-catch.

If the first argument evaluates to true, ASSERT returns NULL.

The ASSERT mechanism can be turned on and off with kernelopts. If turned off, the overhead of processing an ASSERT is negligible.

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

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

$\mathrm{kernelopts}\left(\mathrm{assertlevel}\right)$

$0$

$\mathrm{kernelopts}\left(\mathrm{assertlevel}=1\right)$

$0$

$\mathrm{ASSERT}\left(\mathrm{type}\left(x\,\mathrm{integer}\right)\,''x\; must\; be\; an\; integer''\right)$

Error, assertion failed, x must be an integer

$a≔1\&colon;$$\mathrm{ASSERT}\left(5<a\&comma;\mathrm{cat}\left(''a\; is\; too\; small:''\&comma;a\right)\right)$

Error, assertion failed, a is too small: 1

ASSERT(true,"This is ok");

try ASSERT(false) catch: end try;

Error, assertion failed

kernelopts(assertlevel=0);

$1$

ASSERT(type(x,integer),"x must be an integer");