import Cocoa

/* Create a 3 letter list of the first 6 months of the year */
let months = ["Jan", "Feb", "Mar", "Apr", "May", "Jun"]

/* de-capitalize the list of months */
let lowerMonths = months.map { 
    $0.lowercased()
}

/* print the list of months */
print(lowerMonths)

/* Capitalize the first letter of the list of months */
let capitalizedMonths = months.map { 
    $0.capitalized
}

/* print the list of months */
print(capitalizedMonths)

Output

["jan", "feb", "mar", "apr", "may", "jun"]

["Jan", "Feb", "Mar", "Apr", "May", "Jun"]