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Syntactic noise is a difference between the syntax being used in
the code and the concept it represents in the problem space. In other
words, it is an indication that the code doesn't look the way a naive
programmer might expect it. It is an important metric for
Concept Programming. Since this is a form of noise, it is desirable to reduce it,
but it is in general impossible to completely eliminate it. And also
remember that noise is somewhat subjective, so what is noise to one
person may be music to another.
Here are a few examples of common syntactic noise:
- Statement delimiters such as ; in C, Pascal or Ada, or
parentheses in Lisp, do not represent anything in the problem space. They
address a concern in the problem space of compiler writers at the time the
languages were designed ("how do you parse the input text and sync
on errors?") rather than a concern for the users of those
languages. XL attempts to eliminate as much of these extra
characters as possible.
- Having to use a text-based syntax is often a source of noise
for a number of entities. Development tools like
NeXT/Apple's Interface Builder or
Visual Basic offer
non-textual (graphical) descriptions of many GUI elements, which
reduce syntactic noise.
- Terseness in itself is good (that's why we normally write
1+2 in programs rather than add 1 and 2), but it
really works well only for widely accepted notations. The APL
language, for instance, was known to be very difficult to decipher
because of its over-use of strange operators.
- In C++, so-called angle brackets are used to delimit
template parameters and arguments, as in vector<int>.
This is a productive source of syntactic noise. It causes simple
syntactic ambiguities because >> is also a C++
operator, so the text vector<vector<int>>
doesn't parse right. You need to insert a space, as in
vector<vector<int> >. There are ambiguities
when invoking templates too, as in f<g&&h>(i), which
can be either a set of two comparisons if f is, say, an
integer variable, or an explicit template instantiation with
g&&h as a template argument and i as a run-time
argument if f is a template name.
See the
concept programming analysis of existing languages
for examples combining semantic noise and syntactic noise.
Syntactic noise complicates maintenance of programs, and makes the
learning curve steeper. However, it is important to note that
complicated syntactic rules may make it easier for compilers to
detect and report errors.
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