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9.1. Why Use Limits?

Why use implementation limits at all? Often, a program (ab)uses a
feature in a language to an extent that the implementor did not
foresee. Suppose an implementor decides that variable names can
not be longer than 64 bytes. Sooner or later, a programmer gets
the idea of using very long variable names to encode special
information in the name; maybe as the output of a machine
generated program. The result will be a program that works only
for some interpreters or only for some problems.

By introducing implementation limits, REXX tells the implementors
to what extent a implementation is required to support certain
features, and simultaneously it tells the programmers how much
functionality they can assume is present.

Note that these limited are required minimums for what an
implementation must allow. An interpreter is not supposed to
enforce these limits unless there is a good reason to.