Implement the following simple functions. No libraries are needed to implement them.
Write a function pow(a,b) that returns the value of a ^ b.
You MAY NOT use the built in ^ operator. Remember that by default ^ is only definied in the syntax of Lua, and that the Math library must be incldued for ^ to have meaning. Assume that the Math library is not loaded.
Write a function sigma that takes as it's input an array of numbers, and returns the sum of all the numbers added together. You can assume the array always contains only numbers.
Functions in Lua are quite flexible. Variable numbers of parameters are handled gracefully and functions can return multiple values. The following questions will give you a chance to practice with these abilities.
Write a function longestString that can take up to 4 strings, and returns the longest string.
You may find it helpful to look at the max function discussed in lecture.
Write a function quadratic(a,b,c) that takes the coefficents for an equation of the format \( ax^2 + bx + c = 0 \) and returns the two values of x.
Reminder that the quadratic formula is \( x = \frac{-b \pm \sqrt{b ^ 2 - 4 a c}}{2a} \)
Hint: math.sqrt() is a function in the math library to find a square root.
The Boolean operators in Lua, and and or behave differently than most other programming languages. Remember and returns the first argument when false, while or returns the first argument when true.
For each of the following questions write what the example code does and why.
Example
function f(a, b)
return (a > b) and a or b
end
Answer: The function f returns the maximum between a and b. When (a > b) is false, the and statement will return the first operand, so the statement becomes (a > b) or b. The or operator returns the second operand when the first is false, thus when (a > b) is false, b is returned. When (a > b) is true, the and statement returns a, so the statement becomes a or b. Since a is true, the or operator will return a.
t = {}
function g(t,k)
t[k] = t[k] or 0
end
function h(a)
return (a > 0) and a or -a
end
The Alan M Turing Award is widely considered the most prestiguous award a computer scientist can recieve. It is named in honor of Alan Turing, OBE, one of the founders of computer science and awarded anually by the Association for Computing Machinery. Since last year, the award for the prize has been $1,000,000, the same amount as the Nobel Prize.
For this problem, you will be given a text file in the following format :
1966 Alan Perlis Compilers Yale University 1967 Maurice Wilkes Hardware University of Cambridge
The file is a tab delimited file with the following fields: year of the award, name, area of award, and institution
UPDATE (10/7): You can download it here. or use the following command to get it.
wget http://www.csee.umbc.edu/courses/331/fall15/05/hw/turing.txt
If you are working on GL, wget will not work, so use the following command to directy copy it from my public directory:
cp /afs/umbc.edu/users/b/w/bwilk1/pub/turing.txt .
Read the file into an array of tables.
Hint: The function fromCSV located at the bottom of http://www.lua.org/pil/20.4.html can be modifeid for use with tabs
Sort the table alphabetically by the area of research the award was given for. Print the results in some neat form.
UPDATE (10/1) The update should look something like this:
1975 Allen Newell Carnegie-Mellon University AI 1971 John McCarthy MIT AI 2011 Judea Pearl UCLA AI 1969 Marvin Minsky MIT AI 1975 Herbert Simon Carnegie-Mellon University AI 1994 Raj Reddy Carnegie-Mellon University AI 1994 Edward Feigenbaum Stanford University AI 1986 John Hopcroft Cornell University Algorithms
Sort the table alphabetically by the institution of the winner. Print the results in some neat form.
UPDATE (10/1) The update should look something like this:
1983 Kenneth Thompson Bell Telephone Laboratories Operating Systems 1968 Richard Hamming Bell Telephone Laboratories Coding Systems 1983 Dennis Ritchie Bell Telephone Laboratories Operating Systems 2004 Robert Kahn CNRI Internet 2007 Joseph Sifakis CNRS Model Checking 2007 Edmund Clarke Carnegie Mellon University Model Checking 1975 Herbert Simon Carnegie-Mellon University AI 1975 Allen Newell Carnegie-Mellon University AI
Your homework should be done on the GL systems. For question number 3, submit a text file named hw3.txt. For the other questions, write your answers in a file named hw3.lua.
Submit your homework using the following command:
submit cs331_bwilk1 hw3 hw3.txt hw3.lua
Please test out the submission command before the due date. If you have any problems submitting, email me.