Referring to Something You've Mentioned

When a pronoun appears by itself, it is used as a shorthand for referring to something that has already been mentioned:

e.g.   I bought a box of candy at the store.  It was $1.75.

e.g.   Alice and Bob went on a date.  She looked nice.

There is an important distinction between how pronouns are used in natural languages like English, and how pronouns are used in AutoMathic:

Pronouns in Natural Languages

In unrestricted natural language, the context, number, and gender of a pronoun (as well as unspecified background information) can help remove any ambiguity of what the pronoun refers to, but sometimes the reference can still be ambiguous!

Contextual Clues:

"I bought a box of candy at the store.  It was $1.75."

"I bought a box of candy at the store.  It was crowded."
"I bought a box of candy at the store.  It was already open."

Number Clues:

"I bought safes at the store.  They were not closed."

"I bought safes at the store.  It was not closed."
"I bought safes from two stores.  They were not closed."

Gender Clues:

"Alice and Bob went on a date.  She looked nice."

"Alice and Bob went on a date.  He looked nice."
"Pat and Ashley went on a date.  She looked nice."

Despite the fact that a pronoun's referent can be grammatically ambiguous, people still resolve most ambiguity with their deep understanding of context and real-world knowledge.  AutoMathic has very little understanding of context and essentially no real-world knowledge, so its handling of pronouns is somewhat restricted...

Pronouns in AutoMathic

Even this superficial support of pronouns allows some natural abbreviation of input by avoiding unnatural repetition of nouns.

e.g.   5% of the mass is 39.  What's 23% of it?
                   \________________________/

e.g.   Some number added to half of itself is 21.  What is it?
               \______________________/                    /
                \_________________________________________/

An easy mistake to make is to intend for a pronoun to refer to the most recently mentioned noun phrase instead of the most recently mentioned symbol...

e.g.   The cost is the price plus tax.  How much of that is the tip?
           \               \_ _ _ _ _ _ _ _?_ _ _ _ _/
            \_ _ _ _?_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _/

In the previous example, the speaker probably means for "that" to refer to "the price plus tax" or, the subject of the sentence, "the cost".  Only a deep understanding of context and real-world knowledge leads most people to assume that the pronoun refers to "the price plus tax" or "the cost".

However, the referent of the pronoun is grammatically ambiguous...  The pronoun could also refer to "tax", since "tax" is the most recently mentioned noun:

e.g.   The cost is the price plus tax.  How much of that is the tip?
                                    \________!_______/
AutoMathic interprets pronouns as references to the most recent noun, so it would interpret "that" as a reference to "tax".

To eliminate all reasonable ambiguity, the first sentence could be reworded as follows, ensuring that the pronoun "that" is interpreted as intended:  "that" refers to "the cost", which also happens to be equivalent to the alternate probable referent, "price plus tax":

e.g.   The price plus tax is the cost.  How much of that is the tip?
                                 \___________________/
AutoMathic cannot use the context, number, or gender of a pronoun to resolve ambiguity.  With very few exceptions, AutoMathic interprets pronouns as references to the most recently mentioned noun, not the entire noun phrase!