Code Snippet: Prompt for Yes or No

Within these castle walls be forged Mavens of Computer Science ...

— Merlin, The Coder

Read the contents of a file into a string

Swift

// Prompt the user for 'yes' or 'no'
var line : String?
repeat {
     print("Please enter 'yes' or 'no' ->", terminator:"")
     line = readLine()
} while (line == nil || (line! != "yes" && line! != "no")) 

// By the time we get here, line! is either "yes" or "no"

Python

text = input("Please enter 'yes' or 'no' ->")
while text != "yes" and text != "no":
    text = input("Please enter 'yes' or 'no' ->")