Open Watcom FORTRAN 77 Language Reference
Open Watcom FORTRAN 77 Language Reference
Open Watcom FORTRAN 77 Language Reference
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<strong>Language</strong> <strong>Reference</strong><br />
where:<br />
relop<br />
is a relational operator.<br />
e1, e2 are both arithmetic expressions or both character expressions.<br />
7.3.2.1 Arithmetic Relational Expressions<br />
An arithmetic relational expression is a relational expression in which e1 and e2 are both arithmetic<br />
expressions. An arithmetic relational expression has a value of true if the operands satisfy the relation<br />
specified by the relational operator and false otherwise.<br />
A complex operand is only permitted when using either the .EQ. or .NE. relational operators.<br />
<strong>Watcom</strong> <strong>FORTRAN</strong> <strong>77</strong> allows operands of type COMPLEX*16.<br />
<strong>Open</strong><br />
7.3.2.2 Character Relational Expressions<br />
Character relational expressions are relational expressions whose operands are of type CHARACTER.<br />
The value of a relation between character strings is established by using the collating sequence of the<br />
processor character set. The collating sequence is an ordering of the characters in the processor character<br />
set. Note, for example, that the EBCDIC character set has a different collating sequence than that of the<br />
ASCII character set. For example, e1 is greater than e2 if the value of e1 follows the value of e2 in the<br />
processor collating sequence. The value of a character relational expression depends on the collating<br />
sequence. In the case of the .NE. and .EQ. operators, the collating sequence has no effect.<br />
Example:<br />
IF( ’A’ .LT. ’a’ )THEN<br />
PRINT *, ’The processor character set’<br />
PRINT *, ’appears to be ASCII’<br />
ELSE<br />
PRINT *, ’The processor character set’<br />
PRINT *, ’appears to be EBCDIC’<br />
END IF<br />
END<br />
The above example is a crude test for determining the character set used on your processor.<br />
It is possible to have operands of unequal length. In this case, the character string of smaller length is<br />
treated as if blanks were padded to the right of it to the length of the larger string. The relational operator is<br />
then applied.<br />
7.4 Logical Expressions<br />
Logical expressions are used to describe computations involving operands whose type is LOGICAL or<br />
INTEGER , logical operators and left and right parentheses. The result of the computation is of type<br />
LOGICAL unless both operands are of type INTEGER in which case the result of the computation is of<br />
type INTEGER.<br />
180 Logical Expressions
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