Semicolon in Eiffel

Most of the discussion about semicolon is centered in the languages C or
C++. I think the Eiffel approach to this is very interesting. Below is a
transcript of a section about syntax and the semicolon in the book
"Eiffel: The Language" by Bertand Meyer.


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For syntax, some pragmatism does not hurt. A modern version of the
struggle between big-endians and little-endians provides a good example.
The programming language world is unevenly divided between partisans of
the semicolon (or equivalent) as terminator and the Algol camp of
semicolon-as-delimiter. Although the accepted wisdom nowadays is heavily
in favor of the first approach, I belong to the second school. But in
practice what matters is not anyone's taste but convenience for software
developers: adding or forgetting a semicolon should not result in any
unpleasant consequences.


In th syntax of Eiffel, the semicolon is theoretically a delimiter
(between instructions, declarations, Index_term clauses, Parent parts);
but the syntax was so designed as to make the semicolon syntatically
redundant, useful only to improve readability; so in most contexts it is
optional.


This tolerance is made possible by two syntatical properties: an empty
construct is always legal; and the use of proper construct terminators
(often end) ensures that no new component of a text may be mistaken for
the continuation of the previous construct. For example in


x := y (The recommended style suggests
a := b including a semicolon after y.)


no construct may involve two adjacent identifiers, so that 'a' after 'y'
must begin a new instruction, even without a semicolon.


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Eduardo Issao Ito (knishimo@cat.cce.usp.br)
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