Chapter 10: Physics: Substances, Ropes, Energy and Weight
10.11. Mathematics

It is uncommon, but not absolutely unheard-of, to need to do detailed mathematical calculations in interactive fiction.

The Fibonacci Sequence demonstrates the calculation of a series of numbers; Sieve of Eratosthenes shows off how to calculate the prime numbers within a certain range.

Number Study demonstrates conditional relations between numbers.


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* Example  The Fibonacci Sequence
The modest Leonardo Fibonacci of Pisa will be only too happy to construct his sequence on request, using an array.

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* Example  Sieve of Eratosthenes
The haughty Eratosthenes of Cyrene will nevertheless consent to sieve prime numbers on request.

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* Example  Number Study
The parity and joint magnitude relations explored.

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This is the same case given above, but expanded just slightly to demonstrate that the names of the relations can also be printed, if we like:

"Number Study"

Abstraction is a room.

Parity relates a number (called N) to a number (called M) when N minus M is even.

Joint magnitude relates a number (called N) to a number (called M) when N plus M is greater than 7.

To chart (R - a relation of numbers):
    repeat with N running from 1 to 5:
        repeat with M running from 1 to 5:
            if R relates N to M, say "[N] <=> [M] by [R][line break]";

When play begins:
    let L be { parity relation, joint magnitude relation };
    repeat with R running through L:
        chart R.

As this shows, we can even form lists of relations. The kind of L is "list of relations of numbers".


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