Reverse Polish Notation (RPN) is an arithmetic notation in which the operators follow their operands. It has exactly those facilities which we explicitly provided, and no others. Codechef: reverse Polish Notation. This is the code for reverse polish notation. A Reverse Polish Notation Calculator. Here is the complete program for simulating a reverse Polish notation. 5 This calculator uses the reverse polish notation. 6 */ 7 public class Calculator 8 This week's cartoon is based on the use of RPN or Reverse Polish Notation. This used to be a basic of the computer programmer's world, but today it is not as well known. Hence there may be some perfectly clued up programmers.
RPN Calculator User Manual. RPN Calculator User Manual. Introduction. Anyone who uses the Python interactive command line knows that. Python is a good interactive calculator.
What is reverse polish notation? It means rewriting a mathematical expression into a postfix notation form. For example, '1 + 5 * 2' is rewritten into '1 5 2 *.
However, there are many. Reverse Polish Notation (RPN) for simple. The rpncalc module provides an. RPN that easily integrates with the standard Python.
Features. Supports the standard Python numeric data types (integer, long. Uses the Class Library for. Numbers (CLN) to provide rationals, extended precision floating. Defaults to the CLN numeric.
Requires an explicit conversion to Python float and. Preserves the user's data when exceptions are raised. This helps. the user to debug a calculation or recover from the error and. Division of two integers produces a rational. Supports the Python built- in functions that apply to. Provides extended precision versions of the functions in the.
Allows user installation of additional Python functions. This is. the primary mechanism for programming the calculator. Supports smooth transition between RPN and Python interpreters. In my opinion, Python is a lot easier to. Forth (the classic RPN programming.
I have used Forth and Forth- like languages for over 2. I do not think the RPN interpreter should be turned into yet.
Forth- like language. Leaves the hard things like arrays to the Python interpreter. Much better to simply switch over to the Python.
References. Tutorial. This tutorial presents the concepts needed to operate the RPN.
Extending the interpreter is covered in the Programming section. Before you get started, you.
Follow the instructions in the. Installation section. There is no attempt to teach you how the Python interactive. If you are new to interactive use of Python, you. Python tutorial which is included in the.
Python documentation package. You will want to start with the rpn. This script must be run with the - i switch on the Python. If this is not done, a number of interactive features. In particular, on my Debian box, the command history.
The following command will work on most systems if. As an. example, display the help on the add command. The stack picture shows how. There can be other entries on. The operation has no effect on.
In the above example, the stack picture shows that. Some commands take input from the input stream as well as the.
For these cases, the stack picture has a different form as. If f is the name of a function that computes.
Basic Operations. The simplest way to learn to use the RPN interpreter is to see.
Python interpreter. In the following, you can tell which. The value is removed from the stack by this. Rational numbers are expressed in a more obvious form.
A print statement is required to get Python to print values in. RPN interpreter. Now lets see a couple of math operations in action. Note that I. prefer the ln name to log so it is provided as an alias. This differs from the Python standard. Eventually, it becomes necessary to manipulate the. This section shows the operations that are. Note that these are all borrowed from the Forth.
In order to show the stack effects, another operator is. This operator is extremely useful if you need to see how. There are two options. One is to use an alternate. The. other is to use named variables.
This second alternative is. The alternate stack is another concept borrowed from the Forth. Without this. mechanism, it would be very clumsy to switch back and forth between. The following examples show how to switch between.
In the RPN interpreter, the memory. The following examples show. RPN and. Python interpreters. In order to support polynomials efficiently, it is.
The notation selected has the following form. In other words, a string of polynomial coefficient, exponent.
The exponents must be non- negative integers. The. coefficients can be any numeric format recognized by the number. The number is converted to a constant polynomial.
To illustrate this technique. The rational function is entered as.
The polynomials are. Usually you. simply create an ordinary Python function and install it into the. However, some. terminology will help in explaining what is going on behind the. This terminology is borrowed from the Forth programming.
When a token is extracted from the input stream by the RPN. If the definition is found, the. The called function is responsible. A vocabulary is nothing more than an augmented Python. The dict type is sub classed and a name attribute is. You can get a listing of the search. The system vocabulary.
The user vocabulary is reserved for installing. As an example, we will install a random. The Python function. Python functions for use in the calculator (see the doc string for. The RPN interpreter has a.
Suppose you want to use the equation solver to compute. The following example shows. Note that white space is not allowed. RPN interpreter token. The following. example demonstrates this method. If you need these operations, program your function in. Python and install it.
Use the rpncalc module itself as a source of further examples. You must. install clnum before proceeding. Refer to the clnum user manual for instructions. The simplest way to install rpncalc is to run the distutils. This will install the package in a standard place. Python path. I put it in.
For. example, you may want to uncomment the line that switches the trig. After you get set up, proceed with the Tutorial. History. In the mid 1. I built an interpreter for a language that.
This program. used floating point numbers as its numeric data type. It also. supported programming and was very similar to the Forth programming. It was designed to be extensible in C++. Since it was not. RPN notation, I went looking for a programming environment that was. This lead me to Python circa 1.
Python is also easier to program than. Forth- like languages since you don't need to continuously keep. However, I missed the simplicity of. RPN notation for doing simple calculations. Rather than resurrecting my old interpreter and continuing to. I decided to write the interpreter included in this. This has the added advantage that both RPN and the.
Python interpreter are available.