Open Watcom FORTRAN 77 Language Reference

Language Reference
7.2 Character Expressions
Character expressions are used to describe computations involving operands of type CHARACTER, the
concatenation operator (//) and left and right parentheses. The result of the computation is of type
CHARACTER.
7.2.1 Character Operators
There is only one character operator, namely the concatenation operator (//). It requires two operands of
type CHARACTER. If x is the left operand and y is the right operand, then the result is y concatenated to
x. The length of the result is the sum of the lengths of the two operands. For example, the result of
’AAAAA’//’BBB’
is the string AAAAABBB.
7.2.2 Rules for Forming Character Expressions
The building blocks for character expressions are called character primaries. They are one of the
following.
1. character constant
2. character symbolic constant
3. character variable reference
4. character array element reference
5. character substring reference
6. character function reference
7. ( character expression )
Character expressions are defined as follows:
1. character primary
2. character expression // character primary
A character expression is simply a sequence of character primaries, each separated by the concatenation
operator (//). Rule 2 implies that character primaries are combined from left to right. Except in a character
assignment statement, the operands in a character expression must not contain operands whose length
specification is (*) unless the operand is a symbolic constant.
Note that, unlike arithmetic expressions, parentheses have no effect on the result of evaluating a character
expression. For example, the result of the expressions
and
’A’//’B’//’C’
’A’//(’B’//’C’)
is identically the string ABC.
178 Character Expressions