pseudocode

Exercise 1



Algorithm spur(t, n)

Pre: t :: Train

n :: Integer

Returns: a train

Post: the returned train has the first n cars removed



refToCar rDataOut

for i from 0 to n-1 do

	Dequeue(t, rDataOut)

done

return t





Exercise 2



Algorithm SpurSome(f, n)

Pre: f :: String // naming the file to read

n :: Integer

Returns: a train

Post: the train read from the file named by ‘f’,

and with n cars removed from the front



NEED TO READ THE TRAIN FILE TO
COUNT THE NUMBER OF LINES (NO. OF CARS) AND
SET THIS NUMBER AS nCars


Train* train<-makeTrain(nCars)

readTrain(train, f)

spur(train, n)

return train





Exercise 3




Algorithm shunt(t)

Pre: t :: Train

Returns: a train

Post: the returned train is the original train, but in reverse order



Train* newtrn<-makeTrain(t->nCars) //note that the -> symbol indicates a node nCars of the t Train structure and Train* is the same as refToTrain

refToCar rDataOut		//Car is an element and refToCar just means that it is a reference to Car structure

for i from 0 to nCars-1 do

	PopFromStack(t,rDataOut)

	PushOntoStack(newtrn,*rDataOut)

done

return *newtrain





Exercise 4



Algorithm reverse(f)

Pre: f :: String // naming a file

Returns: a train

Post: the returned train is the one read in, but in reverse order



refToCar rDataOut

NEED TO READ THE TRAIN FILE TO
COUNT THE NUMBER OF LINES (NO. OF CARS) AND
SET THIS NUMBER AS nCars


Train* train<-makeTrain(nCars) // Train* could have been replaced by refToTrain in this pseudocode standard

readTrain(train, f)

shunt(train)

return train



Exercise 5




Algorithm reverseSome(f, n)

Pre: f :: String // naming a file

n :: Integer

Returns: a train

Post: the returned train is the reverse of one read in,

with n cars removed before the reverse



NEED TO READ THE TRAIN FILE TO
COUNT THE NUMBER OF LINES (NO. OF CARS) AND
SET THIS NUMBER AS nCars


Train* train<-makeTrain(nCars) // Train* is the same as refToTrain

train<-spurSome(f,n)

shunt(train)

return train



Exercise 6



Algorithm main()

Pre: a file containing commands in the form of

	spur fname n

	shunt fname n

concerned train files

Post: commands are executed and the resulting trains are added one after the other

in a sequence

Return: boolean showing success or failure