$5\mathrm{.}2$P M $$ Static Type Checking in Ruby

You can do these in Ed or the on$-$campus lab $($or your own computer$).$ For your own computer type: gem install steep then you can run steep.

To use steep in the standard way we need to create two folders.

lib For our code and its input files. In this case this means track.rb and track.txt $($the track data our code reads$)$

sig For the $.$rbs file $($in our case track.rbs$)$ which was produced by typeprof and describes the types in our track.rb program.

Take a look at these two folders in the Ed workshop and make sure you understand what is in each.

Steep will know where to find our program and its RBS type description by looking at a file called Steepfile.

our Steepfile is in the parent directory of lib and sig. Find the Steepfile in the Ed workspace and check its contents $-$ it should look as follows:

The Steepfile file tells steep where to find the code it is checking $($in $./$lib$)$ and the type description $($in $./$sig$).$

Run the steep program in the parent directory in Ed as follows:

You should see the following output:

YOUR TASK: Fix the $.$rbs file so that you produce the following output:

CODE $1$ track.rb :

class Track

attr$\_$accessor :name, :location

def initialize $($name$,$ location$)$

@name $=$ name

@location $=$ location

end

end

# reads in a single track from the given file.

def read$\_$track$($a$\_$file$)$

# complete this function

# you need to create a Track here.

name $=$ a$\_$file.gets

loc $=$ a$\_$file.gets

track $=$ Track.new$($name$,$ loc$)$

return track

end

# Takes a single track and prints it to the terminal

def print$\_$track$($track$)$

puts$("$Track name: #$\{$track$.$name$\}")$

puts$("$Track location: #$\{$track$.$location$\}")$

end

# Open the file and read in the tracks then print them

def main$()$

file $=$ File.new$("$track$.$txt$","$r$")$

track $=$ read$\_$track$($file$)$

file.close

print$\_$track$($track$)$

end

main if $\_\_$FILE$\_\_==$ $$0$ # need this for the testing

CODE track.rbs

# TypeProf $0\mathrm{.}21\mathrm{.}3$

# Classes

class Object

private

def read$\_$track: $($File a$\_$file$)->$ nil

return rea

def print$\_$track: $($Track track$)->$ nil

def main: $->$ nil

end

class Track

attr$\_$accessor name: String?

attr$\_$accessor location: String?

def initialize: $($String$?$ name, String? location$)->$ void

end