package main var manpage = ` NAME rpn - Programmable command-line calculator using reverse polish notation SYNOPSIS Usage: rpn [-bdvh] [] Options: -b, --batchmode enable batch mode -d, --debug enable debug mode -s, --stack show last 5 items of the stack (off by default) -i --intermediate print intermediate results -m, --manual show manual -v, --version show version -h, --help show help When is given, batch mode ist automatically enabled. Use this only when working with stdin. E.g.: echo "2 3 4 5" | rpn + DESCRIPTION rpn is a command line calculator using reverse polish notation. Working principle Reverse Polish Notation (short: RPN) requires to have a stack where numbers and results are being put. So, you put numbers onto the stack and each math operation uses these for calculation, removes them and puts the result back. To visualize it, let's look at a calculation: ((80 + 20) / 2) * 4 This is how you enter the formula int an RPN calculator and how the stack evolves during the operation: | rpn commands | stack contents | calculation | |--------------|----------------|---------------| | 80 | 80 | | | 20 | 80 20 | | | + | 100 | 80 + 20 = 100 | | 2 | 100 2 | | | / | 50 | 100 / 2 = 50 | | 4 | 50 4 | | | x | 200 | 50 * 4 = 200 | The last stack element 200 is the calculation result. USAGE The default mode of operation is the interactive mode. You'll get a prompt which shows you the current size of the stack. At the prompt you enter numbers followed by operators or mathematical functions. You can use completion for the functions. You can either enter each number or operator on its own line or separated by whitespace, that doesn't matter. After a calculation the result will be immediately displayed (and added to the stack). You can quit interactive mode using the commands quit or exit or hit one of the "ctrl-d" or "ctrl-c" key combinations. If you feed data to standard input (STDIN), rpn just does the calculation denoted in the contet fed in via stdin, prints the result and exits. You can also specify a calculation on the commandline. Here are the three variants ($ is the shell prompt): $ rpn rpn> 2 rpn> 2 rpn> + = 4 $ rpn rpn> 2 2 + = 4 $ echo 2 2 + | rpn 4 $ rpn 2 2 + 4 The rpn calculator provides a batch mode which you can use to do math operations on many numbers. Batch mode can be enabled using the commandline option "-b" or toggled using the interactive command batch. Not all math operations and functions work in batch mode though. Example of batch mode usage: $ rpn -b rpn->batch > 2 2 2 2 + = 8 $ rpn rpn> batch rpn->batch> 2 2 2 2 + 8 $ echo 2 2 2 2 + | rpn -b 8 $ echo 2 2 2 2 | rpn + 8 If the first parameter to rpn is a math operator or function, batch mode is enabled automatically, see last example. STACK MANIPULATION There are lots of stack manipulation commands provided. The most important one is undo which goes back to the stack before the last math operation. You can use dump to display the stack. If debugging is enabled ("-d" switch or debug toggle command), then the backup stack is also being displayed. The stack can be reversed using the reverse command. However, sometimes only the last two values are in the wrong order. Use the swap command to exchange them. You can use the shift command to remove the last number from the stack. BUILTIN OPERATORS AND FUNCTIONS Basic operators: + add - substract / divide x multiply (alias: *) ^ power Percent functions: % percent %- substract percent %+ add percent Batch functions: sum sum of all values (alias: +) max max of all values min min of all values mean mean of all values (alias: avg) median median of all values Math functions: mod sqrt abs acos acosh asin asinh atan atan2 atanh cbrt ceil cos cosh erf erfc erfcinv erfinv exp exp2 expm1 floor gamma ilogb j0 j1 log log10 log1p log2 logb pow round roundtoeven sin sinh tan tanh trunc y0 y1 copysign dim hypot Commands: batch toggle batch mode debug toggle debug output dump display the stack contents clear clear the whole stack shift remove the last element of the stack reverse reverse the stack elements swap exchange the last two stack elements show show the last 5 items of the stack history display calculation history help|? show this message quit|exit|c-d|c-c exit program Refer to https://pkg.go.dev/math for details about those functions. INTERACTIVE REPL While you can use rpn in the command-line, the best experience you'll have is the interactive repl (read eval print loop). Just execute "rpn" and you'll be there. In interactive mode you can use TAB completion to complete commands, operators and functions. There's also a history, which allows you to repeat complicated calculations (as long as you've entered them in one line). There are also a lot of key bindings, here are the most important ones: ctrl-c + ctrl-d Exit interactive rpn ctrl-z Send rpn to the backgound. ctrl-a Beginning of line. ctrl-e End of line. ctrl-l Clear the screen. ctrl-r Search through history. COMMENTS Lines starting with "#" are being ignored as comments. You can also append comments to rpn input, e.g.: # a comment 123 # another comment In this case only 123 will be added to the stack. EXTENDING RPN USING LUA You can use a lua script with lua functions to extend the calculator. By default the tool looks for "~/.rpn.lua". You can also specify a script using the -c flag. Here's an example of such a script: function add(a,b) return a + b end function init() register("add", 2, "addition") end Here we created a function "add()" which adds two parameters. All parameters are "FLOAT64" numbers. You don't have to worry about stack management, this is taken care of automatically. The function "init()" MUST be defined, it will be called on startup. You can do anything you like in there, but you need to call the "register()" function to register your functions to the calculator. This function takes these parameters: * function name * number of arguments expected (1,2 or -1 allowed), -1 means batch mode. * help text Please refer to the lua language reference: for more details about LUA. Please note, that io, networking and system stuff is not allowed though. So you can't open files, execute other programs or open a connection to the outside! GETTING HELP In interactive mode you can enter the help command (or ?) to get a short help along with a list of all supported operators and functions. To read the manual you can use the manual command in interactive mode. The commandline option "-m" does the same thing. If you have installed rpn as a package or using the distributed tarball, there will also be a manual page you can read using "man rpn". BUGS In order to report a bug, unexpected behavior, feature requests or to submit a patch, please open an issue on github: . LICENSE This software is licensed under the GNU GENERAL PUBLIC LICENSE version 3. Copyright (c) 2023 by Thomas von Dein This software uses the following GO modules: readline (github.com/chzyer/readline) Released under the MIT License, Copyright (c) 2016-2023 ChenYe pflag (https://github.com/spf13/pflag) Released under the BSD 3 license, Copyright 2013-2023 Steve Francia gopher-lua (github.com/yuin/gopher-lua) Released under the MIT License, Copyright (c) 2015-2023 Yusuke Inuzuka AUTHORS Thomas von Dein tom AT vondein DOT org `