When I try to correct input for my crystal program (in a zsh terminal on my Mac), a ^? character is printed to the screen for each press of backspace. It's disorienting and does not delete any characters from the screen, but it technically functions just fine as I discovered playing around with this little testing snippet.
a = gets.as(String).chomp
puts a
a = gets # alright then^?^?^?^?^?
puts a # alright
What is going on here? How can I make my input behave as a user would expect, is there something special I can do with STDIN?
I think, it will depend on the terminal that you are using and it is largely independent of the programming language (e.g. it has been reported in Python).
Some terminals send ^H or ^? when you type a backslash. I can also reproduce it in xterm (on Linux) when calling cat, which is roughly similar to getting a line and printing it (in a loop):
$ echo $TERM
xterm
$ cat
abc^H^H^Hdef
def
... while it works with other terminals (same test: typing abc, deleting three characters, then typing def):
$ echo $TERM
xterm-256color
$ cat
def
def
You can use libraries like readline to workaround around it. I have not tried it myself, but this library implements bindings for Crystal: crystal-readline