Strings

A string is a sequence of zero or more characters, used to represent some kind of text or message. In fact, a string is really just a list of characters, that is, a value of type List(Char).

A string can be written using the usual syntax for a list of characters, that is,

mystr : List(Char)
mystr = ['h', 'e', 'l', 'l', 'o']

However, this is tedious, so Disco also provides special syntax for strings using double quote marks:

mystr2 : List(Char)
mystr2 = "hello"

In fact, these are exactly the same; the only difference is that mystr2 uses more convenient syntax:

Disco> mystr == mystr2
true

A string can be empty; the empty string is written "". Note that strings can also contain escape sequences. For example, "don\'t \"go\"\naway".

Note the difference between 'x' and "x":

• 'x' is a single character, i.e. a value of type Char.
• "x" is a string, i.e. a value of type List(Char), which just happens to have only a single character.

print command

When a string value is the result of an expression typed at the REPL, it will be displayed in double quotes, with escape sequences to represent special characters. If you want the contents of the string to actually be printed on the screen, interpreting special characters appropriately, you can use the :print command. For example:

Disco> "don\'t \"go\"\naway"
"don't \"go\"\naway"
Disco> :print "don\'t \"go\"\naway"
don't "go"
away

This can be useful to e.g. produce formatted output with multiple lines.