🚀 go-pugleaf

In article <ACHA.91Jan11151418@DRAVIDO.CS.CMU.EDU>, acha@CS.CMU.EDU (Anurag Acharya) writes:
: 
: What is the justification for this "off-side" rule ? The idea of whitespace 
: having semantics is a potential source of inscrutable bugs and, frankly 
: speaking, seems to go against the grain of modern programming language
: design. The concrete syntax of such a language would no longer be context-free,
: let alone LR(1)/LL(1). In fact, I am hard pressed to conceptualize an
: efficient tokenizing algorithm for such languages. 
: 
: Since this rule has also been incorporated into the design of Haskell, it isn't
: just historical and I am sure the designers of Haskell must have had some
: reason(s) for this decision. I would like to know what benefit(s) does this
: rule provide a language deisgner to trade off against the parsing 
: inconvenience and inelegance ? 
: 
I don't think it's really as bad an idea as you make it sound.
At least two other languages use it, ABC and occam.

Certainly indentation makes a program more readable, and once you've
indented correctly the brackets and braces are unnecessary clutter.
What's easier to spot, a missing parenthesis or a missing indentation?

It's a lexical problem not a parsing problem, and it's simple.  At every
newline you have LEX count the leading whitespace, and emit an indent or
an outdent every time it changes.

--Bill Kinnersley