What I want

Text 21 December 2014; idea: many times over a long period

To be understood

What I want is that if by accident I type
dc 15 2 ^ p⏎
or
dc 15 2^p⏎
instead of
dc⏎
15 2^p⏎
, cd makes that calculation anyway and tells me the answer is 225.

Well, I knew the answer already, because in 1973 it was the opinion of our math teacher that we should know at least the squares up until 20 by heart. I took the challenge and I still know them today. No, not really, I’m in doubt about 18 (324?) and 19.

But it was just an example. It’s just that it would be much easier if dc took its calculation instructions not only from stdin but also as command line arguments.

To be always understood

What’s more, I want shells modified (Bourne Shell sh, Born Again Shell bash, Korn Shell ksh and also tcsh) in such a way that when I simply numbers and operators to the command line and end with a p for print, the shell runs dc for me and shows me the result.

Of course it is not going to happen. And I am not going to program any of this weirdness myself.

Reverse

dc is the desk calculator, a very old Unix program. It features arbitrary precision (or in practice: very large, like up to 7000 decimals, just tested on FreeBSD 10.1, no problem!) which normally, hardly anybody needs. But it can do it.

Its instructions dc takes in Reverse Polish Notation (RPN). Number operands are pushed up a stack, and operators pop the operands they need off it and push the result up.

Hewlett Packard hand-held calculators in the 1980, such as the HP41C that I had, worked like that. Recently I read that even modern ones do, although the entry mode is now software switchable between algebraic (1+2=) and RPN (1 2+).

In addition to and beside dc I also often use Windows’ calculator, either in standard view or scientific view, as the case and my actual needs may be. Switching between algebraic and RPN entry doesn’t confuse me.

I’m getting older but I’m still flexible.


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