41 lines
2.1 KiB
Markdown
41 lines
2.1 KiB
Markdown
# Logic
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## Details:
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***Stylised text in <span style="color:green">green</span> represents the actual lift metaphor***
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***<span style="color:red">Red</span> represents significant changes to the program***
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## Initial State:
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* Lifts all at the bottom of the building
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* People all outside the building
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* not waiting on an arrow
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* not in a lift
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## Loop:
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### *These are performed simulataneously, with a thread for each instance*
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---
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* ### Lift Thread - *this is a black-box as far as the metaphor goes*
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1. While there are people to unload at this floor, unload them
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2. Call `get_into_lift(Lift, Direction)`, to load people from the apporopriate waiting queue (up | down) from the current floor
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3. Redraw
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3. Change position
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* `get_into_lift()`
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1. Fetch the correct semaphor for our queue
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2. Get the number of waiting people on that queue
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3. While there are people waiting:
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1. If the lift is empty, change our direction to the supplied direction
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* <span style="color:red">A semaphore is used before the conditional to help ensure the correct value of `in progress` transfers is correct</span>
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2. While the lift is not full, and we have people waiting:
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* <span style="color:red">Keep track of the number of `in progress` waiting people</span>
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1. Add a person to the lift.
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2. Redraw the waiting queue
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3. Remove the person from the waiting queue
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4. Signal person to actually get into the lift
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---
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* ### Person Thread - *this is modelled around the actual metaphor*
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1. Choose a floor to enter
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2. Decide if the floor is above or below the current position
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3. Add ourselves to the appropriate move (up | down) group <span style="color:green">Press the `call elevator` button</span>
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4. <span style="color:green">Wait for the lift to arrive</span> *on the appropriate spot (up | down); no metaphor for this concept*
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5. Enter the lift that is waiting
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6. Move to the waiting group for the target floor <span style="color:green">Press the target floor button</span>
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7. Wait until the lift reaches our destination floor and leave when it is our turn to exit. |