Naming the substitution
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AsTeR chooses identifier names that convey some information about
the object being replaced. This has two advantages:
Names for the substituted expressions are chosen using the
- An identifier like ``summand'' when referring to the expression
appearing as the summand in a summation conveys more information than
the identifier [tex2html_wrap5866].
- When substitutions are spoken after rendering the top-level
expression, the listener finds it easier to relate them
to the top-level expression.
- Type information. The objects returned by the recognizer are
all typed. So at the very least, we have type information for all
objects, e.g., mathematical function, parenthesized expression, etc.
- Contextual information. The first
child of a fraction is called its ``numerator''.
The left-hand side of an implication is
called the ``premise'' and its right-hand side the ``conclusion''. We
have built in this information for standard mathematical objects and
provided a flexible mechanism for the user to add or modify such
- Special patterns: The special patterns presented
in s:special_patterns are also used in synthesizing meaningful
names for the substitutions.
Thus, when substituting for the subscript to a summation operator,
AsTeR uses the name ``lower constraint''.
Since more than one such ``lower constraint'' may be substituted in a general
expression, such names are appended with an integer to make them
unique. This is how the rendering shown earlier for Faa De
Bruno's formula is produced.
Thu Mar 9 20:10:41 EST 1995