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Symbol Substitution may be invoked at any point where the Operator is being
prompted to supply input to an Application Program or anywhere within an
Indirect Command File. The format of the invocation is:-
- Name
- \
where the ``\&" character identifies this as a Symbol Substitution request and
``Name" is the name of the symbol (which may be truncated as long as the symbol
name remains unambiguous). The detection of this syntax will cause UIPACK to
replace this string by the Symbol Equivalence String. The Equivalence String
might itself contain references to other Symbols. Care should be taken to avoid
recursive references. A recursive reference is one where a symbol refers to
itself or to another symbol which refers back to the original symbol. Recursion
will cause the Application to loop indefinitely. UIPACK detects recursion at
substitution time rather than definition time by limiting the number of
symbol substitutions that may take place before an Input Line is exhausted.
This limit is currently set to 16 and if exceeded, will cause an error to be
detected and the Input Stack to be unwound.
Liz Buckle
Fri Jan 13 17:48:27 CST 1995