When the two arithmetic values of differing data type are
compared, a conversion is automatically applied to one of them (as
in arithmetic expressions) to bring it to the type of the other. The
direction of conversion is always:
When comparing integer expressions, there is a considerable difference between the .LE. and .LT. operators, and similarly between .GE. and .GT., so that you should consider carefully what action is required in the limiting case before selecting the appropriate operator.
In comparisons involving the other arithmetic types you should remember that the value of a number may not be stored exactly. This means that it is unwise to rely on tests involving the .EQ. and .NE. operators except in special cases, for example if one of the values has previously been set to zero or some other small integer.
There are two restrictions on complex values: firstly they cannot be compared at all to ones of double precision type. Secondly they cannot use relational operators other than .EQ. and .NE. because there is no simple linear ordering of complex numbers.