Programming For Engineers Chapter 4 Exercises Answer Sheet

Chapter 4 Exercises Answer Sheet 1) Write a script that tests whether the user can follow instructions. It prompts the user to enter an ‘x’. If the user enters anything other than an ‘x’, it prints an error message – otherwise, the script does nothing. Insert your answer here: Ch4Ex1.m % Can the user follow instructions?? inx = input('Enter an x: ', 's'); if inx ~= 'x' fprintf('That was no x!\n') end 2) Write a script that will prompt the user for his or her favorite letter, and then either echo print it or print an error message if the user does not enter a letter. Insert your answer here: Ch4Ex2.m % Prompts user for favorite letter favlet = input('What is your favorite letter: ','s'); if isletter(favlet) fprintf('Cool, your favorite letter is %c\n',favlet) else fprintf('Come on, that''s not even a letter!\n') end 3) Write a statement that will store logical true in a variable named isit if the value of a variable x is in the range from 0 to 10, or logical false if not. Do this with just one assignment statement, with no if or if-else statement! Insert your answer here: isit = x > 0 && x < 10 4) The Pythagorean theorem states that for a right triangle, the relationship between the length of the hypotenuse c and the lengths of the other sides a and b is given by: c2 = a 2 + b 2 Write a script that will prompt the user for the lengths a and c, call a function findb to calculate and return the length of b, and print the result. Note that any values of a or c that are less than or equal to zero would not make sense, so the script should print an error message if the user enters any invalid value. Here is the function findb: findb.m function b = findb(a,c) % Calculates b from a and c b = sqrt(c^2 - a^2); end Insert your answer here: Ch4Ex4.m c = input('Enter the length of c: '); a = input('Enter the length of a: '); if a > 0 && c > 0 b = findb(a,c); fprintf('The length of b is %.1f\n', b) else fprintf('Error in input\n') end 5) Simplify this statement: if val >= 10 disp('Hello') elseif val < 10 disp('Hi') end Insert your answer here: if val >= 10 disp('Hello') else disp('Hi') end 6) In chemistry, the pH of an aqueous solution is a measure of its acidity. The pH scale ranges from 0 to 14, inclusive. A solution with a pH of 7 is said to be neutral, a solution with a pH greater than 7 is basic, and a solution with a pH less than 7 is acidic. Write a script that will prompt the user for the pH of a solution, and will print whether it is neutral, basic, or acidic. If the user enters an invalid pH, an error message will be printed. Insert your answer here: Ch4Ex6.m % Prompts the user for the pH of a solution and prints % whether it is basic, acidic, or neutral ph = input('Enter the pH of the solution: '); if ph >=0 && ph <= 14 if ph < 7 disp('It is acidic') elseif ph == 7 disp('It is neutral') elseif ph > 7 disp('It is basic') end else disp('Error in pH!') end 7) In a script, the user is supposed to enter either a ‘y’ or ‘n’ in response to a prompt. The user’s input is read into a character variable called letter. The script will print “OK, continuing” if the user enters either a ‘y’ or ‘Y’ or it will print “OK, halting” if the user enters a ‘n’ or ‘N’ or “Error” if the user enters anything else. Put this statement in the script first: letter = input('Enter your answer: ', 's'); Write the script using a single nested if-else statement (elseif clause is permitted). Insert your answer here: Ch4Ex7.m % Prompts the user for a 'y' or 'n' answer and responds % accordingly, using an if-else statement letter = input('Enter your answer: ', 's'); if letter == 'y' || letter == 'Y' disp('OK, continuing') elseif letter == 'n' || letter == 'N' disp('OK, halting') else disp('Error') end 8) Write the script from the previous exercise using a switch statement instead. Insert your answer here: Ch4Ex8.m % Prompts the user for a 'y' or 'n' answer and responds % accordingly, using a switch statement letter = input('Enter your answer: ', 's'); switch letter case {'y', 'Y'} disp('OK, continuing') case {'n', 'N'} disp('OK, halting') otherwise disp('Error') end