diff --git a/sources/tech/20190124 Orpie- A command-line reverse Polish notation calculator.md b/sources/tech/20190124 Orpie- A command-line reverse Polish notation calculator.md new file mode 100644 index 0000000000..10e666f625 --- /dev/null +++ b/sources/tech/20190124 Orpie- A command-line reverse Polish notation calculator.md @@ -0,0 +1,128 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Orpie: A command-line reverse Polish notation calculator) +[#]: via: (https://opensource.com/article/19/1/orpie) +[#]: author: (Peter Faller https://opensource.com/users/peterfaller) + +Orpie: A command-line reverse Polish notation calculator +====== +Orpie is a scientific calculator that functions much like early, well-loved HP calculators. +![](https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/calculator_money_currency_financial_tool.jpg?itok=2QMa1y8c) +Orpie is a text-mode [reverse Polish notation][1] (RPN) calculator for the Linux console. It works very much like the early, well-loved Hewlett-Packard calculators. + +### Installing Orpie + +RPM and DEB packages are available for most distributions, so installation is just a matter of using either: + +``` +$ sudo apt install orpie +``` + +or + +``` +$ sudo yum install orpie +``` + +Orpie has a comprehensive man page; new users may want to have it open in another terminal window as they get started. Orpie can be customized for each user by editing the **~/.orpierc** configuration file. The [orpierc(5)][2] man page describes the contents of this file, and **/etc/orpierc** describes the default configuration. + +### Starting up + +Start Orpie by typing **orpie** at the command line. The main screen shows context-sensitive help on the left and the stack on the right. The cursor, where you enter numbers you want to calculate, is at the bottom-right corner. + +![](https://opensource.com/sites/default/files/uploads/orpie_start.png) + +### Example calculation + +For a simple example, let's calculate the factorial of **5 (2 core.md Dict.md lctt2014.md lctt2016.md lctt2018.md LICENSE published README.md scripts sources translated 3 core.md Dict.md lctt2014.md lctt2016.md lctt2018.md LICENSE published README.md scripts sources translated 4 core.md Dict.md lctt2014.md lctt2016.md lctt2018.md LICENSE published README.md scripts sources translated 5)**. First the long way: + +| Keys | Result | +| --------- | --------- | +| 2 | Push 2 onto the stack | +| 3 | Push 3 onto the stack | +| * | Multiply to get 6 | +| 4 | Push 4 onto the stack | +| * | Multiply to get 24 | +| 5 | Push 5 onto the stack | +| * | Multiply to get 120 | + +Note that the multiplication happens as soon as you type *****. If you hit **< enter>** after ***** , Orpie will duplicate the value at position 1 on the stack. (If this happens, you can drop the duplicate with **\**.) + +Equivalent sequences are: + +| Keys | Result | +| ------------- | ------------- | +| 2 3 * 4 * 5 * | Faster! | +| 2 3 4 5 * * * | Same result | +| 5 ' fact | Fastest: Use the built-in function | + +Observe that when you enter **'** , the left pane changes to show matching functions as you type. In the example above, typing **fa** is enough to get the **fact** function. Orpie offers many functions—experiment by typing **'** and a few letters to see what's available. + +![](https://opensource.com/sites/default/files/uploads/orpie_functions.png) + +Note that each operation replaces one or more values on the stack. If you want to store the value at position 1 in the stack, key in (for example) **@factot ** and **S'**. To retrieve the value, key in (for example) **@factot ** then **;** (if you want to see it; otherwise just leave **@factot** as the value for the next calculation). + +### Constants and units + +Orpie understands units and predefines many useful scientific constants. For example, to calculate the energy in a blue light photon at 400nm, calculate **E=hc/(400nm)**. The key sequences are: + +| Keys | Result | +| -------------- | -------------- | +| C c | Get the speed of light in m/s | +| C h | Get Planck's constant in Js | +| * | Calculate h*c | +| 400 9 n _ m | Input 4 _ 10^-9 m | +| / | Do the division and get the result: 4.966 _ 10^-19 J | + +Like choosing functions after typing **'** , typing **C** shows matching constants based on what you type. + +![](https://opensource.com/sites/default/files/uploads/orpie_constants.png) + +### Matrices + +Orpie can also do operations with matrices. For example, to multiply two 2x2 matrices: + +| Keys | Result | +| -------- | -------- | +| [ 1 , 2 [ 3 , 4 | Stack contains the matrix [[ 1, 2 ][ 3, 4 ]] | +| [ 1 , 0 [ 1 , 1 | Push the multiplier matrix onto the stack | +| * | The result is: [[ 3, 2 ][ 7, 4 ]] | + +Note that the **]** characters are automatically inserted—entering **[** starts a new row. + +### Complex numbers + +Orpie can also calculate with complex numbers. They can be entered or displayed in either polar or rectangular form. You can toggle between the polar and rectangular display using the **p** key, and between degrees and radians using the **r** key. For example, to multiply **3 + 4i** by **4 + 4i** : + +| Keys | Result | +| -------- | -------- | +| ( 3 , 4 | The stack contains (3, 4) | +| ( 4 , 4 | Push (4, 4) | +| * | Get the result: (-4, 28) | + +Note that as you go, the results are kept on the stack so you can observe intermediate results in a lengthy calculation. + +![](https://opensource.com/sites/default/files/uploads/orpie_final.png) + +### Quitting Orpie + +You can exit from Orpie by typing **Q**. Your state is saved, so the next time you start Orpie, you'll find the stack as you left it. + +-------------------------------------------------------------------------------- + +via: https://opensource.com/article/19/1/orpie + +作者：[Peter Faller][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://opensource.com/users/peterfaller +[b]: https://github.com/lujun9972 +[1]: https://en.wikipedia.org/wiki/Reverse_Polish_notation +[2]: https://github.com/pelzlpj/orpie/blob/master/doc/orpierc.5