Negation versus Exponential
- To: mathgroup at smc.vnet.net
- Subject: [mg27123] Negation versus Exponential
- From: davidktw at mbox3.singnet.com.sg (David Kwok Tai Wei)
- Date: Sun, 4 Feb 2001 02:58:58 -0500 (EST)
- Organization: The Math Forum
- Sender: owner-wri-mathgroup at wolfram.com
I have a very simple question here
should Negation (~) have a lower precedence than Exponential
becoz if that's the case, ~1^2 should be evaluated as -1 instead of 1.
-1 is incorrect becoz when I calculate ~1^2, I don't use brackets at
all. so why must I explicitly bracket the expression --> (~1)^2, just
to overcome the fault, that negation should be of higher precedence
when dealing with infix expression, computers will usually convert to
postfix expression b4 evaluating them.
hence a^~f will yield the postfix of a^f~, provided negation is of
lower precedence than exponential.
looking at the postfix, if I try to evaluate it using a stack, it will
generate error becoz when I try to evaluate ^ and pop 2 operands from
the stac, only one is available.
On the other hand, if I set negation of higher precedence than
exponential, all such errors will be solved.
So why stick to the old convention where it's wrong. It's such a
Please reply me by emailing to davidktw at mbox3.singnet.com.sg
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