ex. 24 asks to "Write the function (authors books) that returns the authors of every book in books as a set." but later on after ex. 30 "(def authors #{china, felleisen, octavia, friedman})" data is introduced for testing purposes which gets masked by the previous function definition.
ex. 24 asks to "Write the function (authors books) that returns the authors of every book in books as a set." but later on after ex. 30 "(def authors #{china, felleisen, octavia, friedman})" data is introduced for testing purposes which gets masked by the previous function definition.