Copying antifeatures: multiline strings

Multiline strings are a Good Thing but they usually end up implemented just a little bit wrong.

Delimiters

First, they require special delimiters. Most grammars could easily allow ordinary strings to break across lines, and many languages could even add this in a backward-compatible way. A string that includes line breaks is no harder to parse than a single-line string:

foo = "
Hello
world
"

To the great annoyance of programmers everywhere, languages generally require special delimiters for multiline strings:

foo = """
Hello
world
"""

Thus, when we find ourselves typing a string literal and the line gets uncomfortably long, the language makes us go back to the beginning and change delimiters. Vice versa when shortening strings.

Indentation

Most multiline strings end up being indented. Ruby gets multiline string quote style right, but fails on indentation:

def do_stuff()
   foo = "
     hello
     world
     "
   return foo
end

puts do_stuff() # "\n    hello\n    world\n    "

What are those leading spaces doing? I can’t think of a time when I’ve ever wanted a string literal to maintain its source indentation at runtime.

Almost always, multiline strings fall into two categories:

Indentation is irrelevant Needs trim and dedent
sql = "
  select *
  from foo
  where bar
    and baz "
help = "
   usage: frob [-nicate]
     frob the widget
   
   -n turn on the n
"

So there are many use cases where trimming and dedenting is warranted, but almost none where it hurts.

CoffeeScript almost got both aspects right, but it makes a distinction between “multiline strings”, that use ordinary quotes and “block strings,” which use triple-quotes. Ordinary strings collapse line breaks to single spaces, triple-quoted strings trim and dedent correctly.

Next time: the perils of such subtle distinction in quote style.

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