CSE 110 - Homework 8

CSE110 Spring 2001

Homework #8

Friday the 20th of April at 5pm

Note: bold text in the examples is input from the user.

[25 points] You can look all you want at the delicate musculature of a seaworthy crab, or the intricate filigree of a splendid drum of resins, but while you revel in life's rich pageant, Ringo is blind to all but the most obtuse observations. Oh sure, he can tell what part of the ocean he's in, but the play of light on a disappearing mess of smelts or the subtle reek of an over-ripe carrotfish are all but lost on him.
It's about time you set up an `e(x)amine' command, which prints a description of whatever object Ringo is holding:
- Create a new type ObjectDescription that contains two string fields, one for the name of an object and one for a short description.
- In main, create an array of type ObjectDescription of size 100 (or the same size as your ObjectInfo array). Initialize one array location for each object with the object's name and its description.
- Add a new field to the ObjectInfo structure that has type pointer to ObjectDescription. When initializing all of the rest of the fields for the ObjectInfo structure of each object, also get a pointer to its corresponding ObjectDescription structure and assign it to the new field you just added. Note that you will also need to make sure you copy this new field over in any place in your code that makes a copy of a ObjectInfo structure - your Move function might do this, and possibly Grab and Throw as well. Look over them carefully to see if any changes are needed.
- Add an action `x' to your switch statement in main. Write the code that checks to see if anything is in Ringo's hand, and if there is, prints out the name and description of the object that Ringo is holding. This is not to say that you have to write a function, but it is natural to do so. The function would probably have this prototype:
```
void Examine(ObjectInfo objs[MAX_OBJS]);
```
The simulation should then print the description of whatever object Ringo is holding on any input of `x'.
Example:
```
% a.out
You're in an octopus' garden, just like in your song, except the octopus is
throwing things at you and frightening you.
Your action: g
You grab the octopus with your mighty European arms.
The crab swims south, out of the crabs cottage, into the eels estates.
Your action: t
You throw the octopus onto the ground.  It is momentarily dazed.
The crab swims east, out of the eels estates, into the empty sea.
Your action: e
You swim east, out of the octopus' garden, into the eels estates.
The crab tries to swim east, out of empty sea, but the current draws it back.
Your action: g
You grab an eel.
The crab swims west, out of the empty sea, into the eels estates.
Your action: x
  You have a luscious electric eel in your hand.  It runs on three 
  `D' batteries and fills your nerves with tingly electricity, and  
  there's some delicate musculature on it somewhere.
The crab swims south, out of the eels estates, into the marine refinery.
Your action: q
You quit, bored of undersea life already.
```

[30 points] And how is Ringo going to know what to examine if he doesn't know which objects are in his vicinity? Add support for a command (l)ook, using a function that matches the following prototype:

void Look ( ObjectInfo objects[100] ) ;

which should search the array that's given as its argument for all objects at Ringo's current location (except for Ringo himself), and print a message for each object X like this:

There is an X here.

It is fine to print a line for each object if there's more than one object (the example implementation does something a bit fancier, printing a comma-separated list of objects, but you need not do that). Then, add a new action `l' to the switch statement in main and call your Look function on that action. The function should use only the ObjectInfo array elements and the ObjectDescription structures that they point to. It should not use a large conditional statement (such as a switch case) containing several constant printf statements. Your simulator should also call this Look function on every movement action (i.e. `n', `s', `e' or `w'), so Ringo doesn't have to explicitly (l)ook every time he moves.

Example:

% a.out
You're in an octopus' garden, just like in your song, except the octopus is
throwing things at you and frightening you.
  There is an octopus here.
Your action: g
You grab the octopus with your mighty European arms.
The crab swims south, out of the crabs cottage, into the eels estates.
Your action: t
You throw the octopus onto the ground.  It is momentarily dazed.
The crab swims east, out of the eels estates, into the empty sea.
Your action: e
You swim east, out of the octopus' garden, into the eels estates.
  There is an eel here.
The crab swims north, out of the empty sea, into the yellow submarine.
Your action: s
You swim south, out of the eels estates, into the marine refinery.
  There is a drum here.
  There is a drum here.
  There is a drum here.
  There is a drum here.
  There is a drum here.
  There is a drum here.
  There is a drum here.
  There is a drum here.
  There is a drum here.
  There is a drum here.
  There is a drum here.
  There is a drum here.
The crab swims south, out of the yellow submarine, into the empty sea.
Your action: q
You quit, bored of undersea life already.

[30 points] One day Ringo was entertaining the eels by banging on a drum of refinery by-products. He is a famous drummer, you know. When he finished, he threw down the drum (command `t') and yelled at them to go home and watch television (command `y'), but when Ringo tried to pick up the drum again to take it back to the refinery (command `g'), he wound up with a handful of eels instead -- how gauche! Ringo holds you responsible.

Change your simulator so that it allows Ringo to specify the name of the object he wants to pick up, so he doesn't risk this kind of fiasco again if there is more than one object in the same area. If Ringo gives a `g' (grab) command, your program should read another string of characters from the input line, and compare it to the name of each object at Ringo's location. The first object with a matching name should be moved to Ringo's hand. Just as in the previous problem, the code that does this should use only the ObjectInfo array elements and the ObjectDescription structures that they point to. It should not use a large conditional statement (such as a switch case) containing several constant printf messages.

If the action is g, read in a space followed by a string that specifies the object to be grabbed.
Add a string argument to your Grab function. Pass the string you read in, above, as this new argument.
Modify the body of your grab function so that it not only finds objects that are at Ringo's current location, but also finds and object whose name (stored in its ObjectDescription structure) matches the string that was passed as Grab's new argument. The string matching should be case insensitive.

Example:

% a.out
You're in an octopus' garden, just like in your song, except the octopus is
throwing things at you and frightening you.
  There is an octopus here.
Your action: g octopus
You grab the octopus with your mighty European arms.
The crab swims east, out of the crabs cottage, into the yellow submarine.
Your action: t
You throw the octopus onto the ground.  It is momentarily dazed.
The crab swims north, out of the yellow submarine, into the Micky Dolens' locker.
Your action: s
You swim south, out of the octopus' garden, into the stolen puppets.
  There is nothing interesting here.
The crab swims west, out of Micky Dolens' locker, into the spooky sinkhole.
Your action: e
You swim east, out of the stolen puppets, into the marine refinery.
  There is a drum here.
  There is a drum here.
  There is a drum here.
  There is a drum here.
  There is a drum here.
  There is a drum here.
  There is a drum here.
  There is a drum here.
  There is a drum here.
  There is a drum here.
  There is a drum here.
  There is a drum here.
The crab swims east, out of the spooky sinkhole, into the Micky Dolens' locker.
Your action: g drum
You grab a drum.
The crab swims south, out of Micky Dolens' locker, into the yellow submarine.
Your action: n
You swim north, out of the marine refinery, into the eels estates.
  There is an eel here.
The crab swims south, out of the yellow submarine, into the empty sea.
Your action: t
You throw a drum onto ground.
The crab swims south, out of the empty sea, into the barnacle pile.
Your action: l
You look around...
  There is an eel here.
  There is a drum here.
The crab swims west, out of the barnacle pile, into the marine refinery.
Your action: y
You yell, "go watch TV!"
The crab swims west, out of the marine refinery, into the stolen puppets.
Your action: g drum
You grab drum.
The crab swims north, out of the stolen puppets, into the octopus garden.
Your action: l
You look around...
  There is an eel here.
The crab swims north, out of the octopus' garden, into the brine & spirits.
Your action: q
You quit, bored of undersea life already.