The condition expr1 =
expr2 tests whether the
expressions expr1 and expr2 are equal. There are several
possibilities:
For nested structures, equality is tested recursively.
If expr1 and expr2 do not have the same type, the test
results in an error; only the symbol nil
can be compared to any value.
The comparison expr1 /=
expr2 holds iff the
comparison expr1 =
expr2 does not hold.