How to read syntax diagrams
Throughout this document, diagrams illustrate XL Fortran syntax. You can
use this section to help you to interpret the syntax diagrams.
If a variable or user-specified name ends in _list, you can provide
a list of these terms separated by commas.
You must enter punctuation marks, parentheses, arithmetic operators, and
other special characters as part of the syntax.
- Read syntax diagrams from left to right and from top to bottom, following
the path of the line:
- The >>--- symbol indicates the beginning of
a statement.
- The ---> symbol indicates that the statement syntax
continues on the next line.
- The >--- symbol indicates that a statement continues
from the previous line.
- The --->< symbol indicates the end of a statement.
- Program units, procedures, constructs, interface blocks and derived-type
definitions consist of several individual statements. For such items, a box
encloses the syntax representation, and individual syntax diagrams show the
required order for the equivalent statements.
- IBM(R) and Fortran 95 extensions are marked by a number in the syntax diagram
with an explanatory note immediately following the diagram.
- Required items are shown on the horizontal line (the main path):
 >>-keyword--required_argument----------------------------------><
|
- Optional items are shown below the main path:
 >>-keyword--+-------------------+------------------------------><
'-optional_argument-'
|
Note:
Optional items (not in syntax diagrams) are enclosed
by square brackets ([ and ]). For example, [UNIT=]u
- If you can choose from two or more items, they are shown vertically, in
a stack.
If you it is required that you choose at least one
of the items, one item of the stack is shown on the main path:
 >>-keyword--+-required_argument-+------------------------------><
'-required_argument-'
|
If choosing one of the items is optional, the entire stack is
shown below the main path:
 >>-keyword--+-------------------+------------------------------><
+-optional_argument-+
'-optional_argument-'
|
- An arrow returning to the left above the main line (a repeat arrow) indicates
that you can repeat an item, and the separator character if it is other than
a blank:
 .-,-------------------.
V |
>>-keyword----repeatable_argument-+----------------------------><
|
A repeat arrow above a stack indicates that you can make more
than one choice from the items in the stack.
 .-,---------------------.
V |
>>-keyword----+-required_argument-+-+--------------------------><
'-required_argument-'
|