5.1.3 Comparing expressions

Expressions can be compared with the usual C++ relational operators like ==, >, and < but if the expressions contain symbols, the result is usually not determinable and the result will be false, except in the case of the != operator. You should also be aware that GiNaC will only do the most trivial test for equality (subtracting both expressions), so something like (pow(x,2)+x)/x==x+1 will return false.

Actually, if you construct an expression like a == b, this will be represented by an object of the relational class (see section Relations) which is not evaluated until (explicitly or implicitly) cast to a bool.

There are also two methods

bool ex::is_equal(const ex & other);
bool ex::is_zero();

for checking whether one expression is equal to another, or equal to zero, respectively. See also the method ex::is_zero_matrix(), see section Matrices.