Sometimes you want to write some text slightly differently if the
chapter is a stand-alone document compared to the case when it is
part of a book. Mako if tests are ideal for this. Suppose you
introduce a Mako variable ALONE that is true/defined if the chapter
is a stand-alone document and false/undefined if part of a book. Then
you can simply write
In this
% if ALONE:
rather small
% else:
large
% endif
${BOOK}
doconce format with the option -DALONE will turn ALONE to
true and the output is typically
In this rather small document
-DALONE as argument to doconce format,
which makes ALONE undefined, and we
get the output
In this large book
Mako variables can be defined/undefined (boolean variables) or be standard strings:
% if SOME_STRING_VARIABLE in ('value1', 'value2'):
some running text
% endif
...
% if not SOME_BOOLEAN_VARIABLE:
some other running text
% else:
yet more different text
% endif
With Mako variables, you can easily comment out large portions of text by testing on some variable you do not intend to define:
% if EXTRA:
This is
text that
will never
appear in the
output.
% endif
Also, it is straightforward to write more than one version of a chapter. For example, you may want to produce a version of a chapter that is tailored to a specific course, while you for general publishing on the Internet want a more general version, and maybe a third version when the chapter is included in a book for the international market. All this is easily done by if tests on appropriately defined Mako variables
% if COURSE == 'IT1713':
# Specific text for a course IT1713
...
% elif COURSE == 'IT1713b':
# Specific text for a the special IT1713b variant of the course
...
% elif COURSE == 'general':
# General text when the chapter is a stand-alone document
...
% elif COURSE == 'book1':
# Text when course is a part of a particular book
...
% elif COURSE == 'book2':
# Text when course is a part of another book
...
% endif