Re: Syntax directed program editing

In article 92-02-024 richard@harlqn.co.uk (Richard
Brooksby) writes:


>Why aren't there more editors which operate directly on the parse trees of
>languages? Are there fundamental problems with this approach?


Yes. Actually, despite the moderator's comments, it works
reasonably well for some languages, like Pascal, for which the textual
form of the program is verbose, so that it's worth spending some time to
economise on keystrokes; it's hopeless for terse languages like C.


The first problem with *any* syntax-directed editing is that the
user needs to understand the syntax of the language being written. This
is not as common as it ought to be, especially for the beginners who
might, in principle, benefit most from a helpful editor.


The second problem is that the syntax that a compiler would like
to use [and that is usually the syntax by which the language is defined]
is different from the syntax that a helpful syntax-directed editor should
use. Example: the compiler would probably like to treat all standard
functions and procedures in the same general way as user-defined ones; we
found it much more helpful if they were presented to the user as special
forms of statement or expression.


--
Andy Walker, Maths Dept., Nott'm Univ., UK.
anw@maths.nott.ac.uk
[How do you handle changes like moving a statement across an "end" ? -John]
--

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