lew@ihuxr.UUCP (Lew Mammel, Jr.) (12/07/84)
Some time ago I wrote a simple desk calculator for myself using Yacc and Lex, as suggested by the example in the Yacc document. My excuse was that I wanted a simple floating point capability, with trig and fractional powers, which dc and bc don't provide. I also provided for arbitrary length variable names; a huge improvement over bc in my opinion. Some time later, I enhanced it with a formula definition capability. I can type a line like: #define alpha "(1 - beta^2)^.5)" Then, whenever I type "alpha" (not including quotes of course) it is expanded into the formula. It works by saving the string and then "unputting" it into the input stream when the defined token is read. It took me a while to get this scheme straight in my own mind, but when I finally did I found that Lex was ready and waiting for me with just the right function. It was quite simple to implement. Since it unputs the defined strings into the actual input stream, nested substitution works with no sweat. There is no guard against self-definition, however, which causes "yacc stack overflow". I can put a bunch of these definitions in a file and use them in an interactive session with the command line: cat file.defs - | calc I used a file like this when I did some calculations on the brightness of venus: #define PI "3.1415926535" #define theta "t*PI/180" #define x "((1+A^2-2*A*cos(theta))^.5)" #define b "((A+x)^2-1)/2/A/x^3" A=.723 With these initializations I can type say, "t=45" then type "b", and the defined value of "b" will be displayed. I can then alter "A" by typing say, "A=.5" and then see the new value of "b" by typing "b" again. I should mention that the results I posted to net.astro were from a C program, but I used my calculator for "messing around" with the formula. I have found this convenient to use, and as I said, it was very easy to implement. Since it's written in Yacc and Lex, alterations and enhancements can be made easily, as well. Lew Mammel, Jr. ihnp4!ihuxr!lew P.S. This is my last day on ihuxr. I'll be at ihnp4!ihlpa soon, but net and mail availability may be shaky for a while.
gwyn@brl-tgr.ARPA (Doug Gwyn <gwyn>) (12/09/84)
> Some time ago I wrote a simple desk calculator ...
Gee, Lew, sounds amazingly like "hoc", whose source is in Kernighan & Pike.perlman@wivax.UUCP (Gary Perlman) (12/09/84)
UNIX|STAT, my public domain stat packagge has a similar calculator. Looking at the sender's address, I guess the one recently described is not. > Some time ago I wrote a simple desk calculator for myself using Yacc and > Lex, as suggested by the example in the Yacc document. My excuse was that > I wanted a simple floating point capability, with trig and fractional > powers, which dc and bc don't provide. I also provided for arbitrary length > variable names; a huge improvement over bc in my opinion. My calc has all of these. > Some time later, I enhanced it with a formula definition capability. > I can type a line like: > > #define alpha "(1 - beta^2)^.5)" > #define PI "3.1415926535" > #define theta "t*PI/180" > #define x "((1+A^2-2*A*cos(theta))^.5)" > #define b "((A+x)^2-1)/2/A/x^3" > A=.723 my calc differs by using name=definition format, and it stores the parse tree so it should be more efficiient. More info on calc and UNIX|STAT can be obtained from the address below. Gary Perlman Wang Institute Tyng Road Tyngsboro, MA 01879 USA (617) 649-9731
rwl@uvacs.UUCP (Ray Lubinsky) (12/12/84)
> > Some time ago I wrote a simple desk calculator ... > > Gee, Lew, sounds amazingly like "hoc", whose source is in Kernighan & Pike. ------------------------------------------------------------------------------ Speaking of 'hoc', has anybody copied the thing from Kernighan & Pike and gotten it to run? I'm 99.99% sure that I've caught all the typos, but I find that my compiled version cannot perform 'procedure' or 'function' definitions properly? Post or mail a response as you see fit. Thanks! ------------------------------------------------------------------------------ Ray Lubinsky University of Virginia, Dept. of Computer Science uucp: decvax!mcnc!ncsu!uvacs!rwl