- expr1 and expr2 represent expressions

- The operator != evaluates to true iff its operands expr1 and
expr2 are syntactically unequal and both different from error,
constant expressions that are not constants and that evaluate to two
different floating-point number with the global precision prec or
polynomials that are unequal while automatic expression simplification
is activated. The user should be aware of the fact that because of
floating-point evaluation, the operator != is not exactly the
same as the negation of the mathematical equality. Further, expressions
that are polynomials may not be structurally equal when != evaluates
to false; in order to obtain purely structural tests, the user should
deactivate automatic simplification using autosimplify.

Following the IEEE 754 standard, NaN compares unequal to itself, even though this corresponds to a case when expr1 and expr2 are syntactically equal and different from error. Accordingly, the interval [NaN, NaN] compares unequal to itself.

Note that the expressions !(expr1 != expr2) and expr1 == expr2 do not always evaluate to the same boolean value. See error for details.

false

> "Hello" != "Salut";

true

> "Hello" != 5;

true

> 5 + x != 5 + x;

false

false

> asin(1) * 2 != pi;

false

> exp(5) != log(4);

true

true

The precision has been set to 12 bits.

> 16384.1 != 16385.1;

false

true

> [NaN,NaN] != [NaN,NaN];

true

> error != error;

false

> q = x * (1 + x);

> autosimplify = on;

Automatic pure tree simplification has been activated.

> p != q;

false

> autosimplify = off;

Automatic pure tree simplification has been deactivated.

> p != q;

true