Com S 541 Lecture -*- Outline -*-

* lexical matters in Haskell (Thompson 3.7, Davie 2.14, appendix C.2-3)

** identifiers and operators (Thompson 1.7, Davie 2.14.2)
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             IDENTIFIERS

identifiers (non infix):

    examples
	pythag, fac, x, y

    notes
	1. case matters
	2. start with lower-case letter
	3. must start with lower-case
		letter, unless constructor
			or a type

		identifier, Cons, Typ

	4. can use letters, digits, primes
		and underscores (_)

		f', x_squared, x3'n_
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		OPERATORS

operators (infix):

    examples
	+, -, !!, :, ++, ==

    notes
	1. Drawn from: !#$%&*+./<=>?@\^|:
	2. A constructor if start with :
	3. Any identifier can be made into
	   an operator using backquotes

		3 `div` 4
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** layout (Thompson 3.7, 6.3, Davie 2.14.3)
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	    LAYOUT MATTERS

	let x = 3
	    y = 4
	in x + y

  ==>

	let {x = 3
	    ;y = 4
	}in x + y



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	simplified rules:
		; inserted at same indentation
		} inserted when indented to left

	You can write with the { and ; and } if you want, all on one line...

	Watch out, you can get syntax errors from bad indentation!