Commit 94dfec4598f9418b688c5600f4e2d7cb98b9f221 - Wanda

Some edits. Chris Pressey 6 years ago

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0	0	Wanda
1	1	=====
2	2
3		Wanda is a Forth-like language. Despite being Forth-like, it seems unfair
4		to call it "concatenative", or even "stack-based", because it is based
5		on a string-rewriting semantics.
	3	Wanda is a "concatenative" language that's not actually "concatenative"
	4	at all, nor even "stack-based", because it's based on a string-rewriting
	5	semantics.
6	6
7	7	The remainder of this document will describe the language and will attempt
8	8	to justify the above statement.

41	41	pattern `X Y $ +`, where X and Y are integers; the part of the string that
42	42	matches that pattern is replaced by a single integer which is the sum of
43	43	X and Y, followed by a `$`.
44
45		If no patterns match anywhere in the string, the expression remains unchanged
46		and evaluation terminates.
47
48		2 $ +
49		===> 2 $ +
50	44
51	45	You can think of `$` as a symbol which delineates the stack (on the left)
52	46	from the program (on the right). When constants are encountered in the

59	53	stack, nor an instruction that pushes the value 2 onto the stack; it's just
60	54	a `2`.
61	55
	56	Indeed, observe that, if no patterns match anywhere in the string, the
	57	expression remains unchanged and evaluation terminates:
	58
	59	2 $ +
	60	===> 2 $ +
	61
62	62	### Some other builtins
63	63
64		We've seen `+` and `*`, which are built-in rules.
65		There are a couple of other built-in rules.
	64	We've seen `+` and `*`, which are built-in functions (or rules).
	65	There are a couple of other built-in functions (or rules).
66	66
67	67	$ 7 sgn 0 sgn -14 sgn
68	68	===> 1 0 -1 $