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Re: Stack-based syntax (was: affixes)

From:Mark J. Reed <markjreed@...>
Date:Thursday, February 24, 2005, 19:04
On Thu, Feb 24, 2005 at 06:34:21PM +0000, Ray Brown wrote:
> >And certainly there must be some "lexical" information in the - and ÷ > >operators, which enforce an ordering on their operands? > > In the case of + the ordering is irrelevant, tho in the case of - it is > not. But the ordering is surely the result of stack structure itself, not > the operator per_se.
Right. Now consider a system which has only + and ×, but also has a unary NEGATE and a unary INVERT. Then those latter two would be the equivalent of the unary case markers I mentioned: 3 2 NEG + = 1 3 NEG 2 + = -1 On the other hand, if there were no such operators but literals could be negative or fractional, then 3 -2 + = 1 -3 2 + = -1 And now you have the case marking within the operand itself.
> The literal 5 is of the same type as 3 and 2; the notion of > additionality is not there in the resultant evaluation. But when a > Fithian verb operates upon its arguments, surely the meaning of the > verb forms part of the resultant meaning?
Sure, but this is really a use/mention distinction that is based on only one possible process in the arithmetic example. So change what we're doing - instead of evaluating the expression, let's transform it to infix. The stack then holds infix expressions, not just numbers: 1 2 + 3 - 4 × 5 ÷ push 1, push 2, pop 2, pop 1, push (1 + 2), push 3, pop 3, pop (1+2), push ((1 + 2) - 3), push 4, pop 4, pop ((1 + 2) - 3), push (((1 + 2) - 3) × 4), push 5, pop 5, pop (((1 + 2) - 3) × 4), push ((((1 + 2) - 3) × 4) ÷ 5). That's a better analogue to the mental translation of RPNglish to English in my original message. -Marcos

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Ray Brown <ray.brown@...>