In Haskell, you can convert a string to an integer using the read function. The read function takes a string as an argument and returns a value of a specific type based on the context in which it is used.
To convert a string to an integer, you can use the read function along with the :: syntax to specify the specific type of integer you want the string to be converted to. Here is an example:
-- Convert a string to an Integer
stringToInt :: String -> Integer
stringToInt str = read str :: Integer
In this example, stringToInt is a function that takes a string as a parameter and returns an integer of type Integer. The read function is used to convert the string to an integer, and the :: Integer syntax is used to specify that the resulting value should be an Integer. Here are some examples of the stringToInt function in action:
-- Convert the string "123" to an Integer
stringToInt "123" -- Returns 123
-- Convert the string "-456" to an Integer
stringToInt "-456" -- Returns -456
-- Convert the string "abc" to an Integer (will throw an exception)
stringToInt "abc" -- Throws an exception because "abc" is not a valid integer
It's important to note that the read function can throw an exception if the string cannot be parsed as an integer. In the last example above, stringToInt "abc" would throw an exception because "abc" is not a valid integer. To avoid this, you can use the readMaybe function from the Text.Read module, which returns a Maybe value instead of throwing an exception.