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Learning Exercise
The |> operator is called the pipe operator. It can be used to chain function calls together in such a way that the value returned by the previous function call is passed to the next function call.
"hello"
|> string.uppercase
|> string.append("?!")
// -> "HELLO?!"
The above code is equivalent to the following:
string.append(string.uppercase("hello"), "?!")
The pipe operator will either pass the value as the first argument to the function call, or the only argument to a new call, selecting whichever would have the correct type.
100
|> function_that_takes_two_arguments(1)
// Is equivalent to
function_that_takes_two_arguments(100, 1)
100
|> function_that_returns_a_function(1)
// Is equivalent to
function_that_returns_a_function(1)(100)
Sometimes we want to pass the value into another position, in this case the _ placeholder can be used to indicate where the value should be inserted.
100
|> some_function(1, _, 2)
In this exercise, you are going to help high school sweethearts profess their love on social media by generating an ASCII heart with their initials:
****** ******
** ** ** **
** ** ** **
** * **
** **
** J. K. + M. B. **
** **
** **
** **
** **
** **
** **
***
*
Implement the first_letter function. It should take a name and return its first letter. It should clean up any unnecessary whitespace from the name.
first_letter("Jane")
// -> "J"
Implement the initial function. It should take a name and return its first letter, uppercase, followed by a dot. Make sure to reuse first_letter that you defined in the previous step.
initial("Robert")
// -> "R."
Implement the initials function. It should take a full name, consisting of a first name and a last name separated by a space, and return the initials. Make sure to reuse initial that you defined in the previous step.
initials("Lance Green")
// -> "L. G."
Implement the pair function. It should take two full names and return the initials inside an ASCII heart. Make sure to reuse initials that you defined in the previous step.
pair("Blake Miller", "Riley Lewis")
// -> "
// ****** ******
// ** ** ** **
// ** ** ** **
// ** * **
// ** **
// ** B. M. + R. L. **
// ** **
// ** **
// ** **
// ** **
// ** **
// ** **
// ***
// *
// "
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