Writing a command line interpreter in java

Further Reading Command-Line Argument Processing There are a number of command-line options and environment variables that can affect the performance characteristics of the Java HotSpot Virtual Machine. There are three main categories of options: Standard options are expected to be accepted by all JVM implementations and are stable between releases though they can be deprecated. Options that begin with -X are non-standard not guaranteed to be supported on all JVM implementationsand are subject to change without notice in subsequent releases of the Java SDK.

Writing a command line interpreter in java

For reference, I have put an implementation of an AEL interpreter online. The Lexer The lexer takes text input and returns a list of tokens. We will have a variable c which corresponds to the current character, create a function called advance to step forward one character in the input and return the next character, and a function called addToken which appends a token to the list of tokens.

The Parser There are lots of different strategies for writing a parser. One of the most common is writing a Backus-Naur grammar and using recursive descent. In this article, we will be using a somewhat less common strategy called operator-precedence parsingusing techiques described Douglas Crockford's Top Down Operator Precedence article.

Shell script - Wikipedia

Operator precedence parsing begins with the following process Associate every operational token with a left binding power, and an operational function. If the operator does not manipulate the tokens on its left such as the unary -associate it with a null denotative function hereafter abbreviated as nud.

Identifiers and numbers also have a nud function associated with them. After this is done, it can start to generate the parse tree.

Crash course in PEG.js grammar definitions

To show how this works, I'll use the arithmetic expresion below as an example. This is the end of the list of tokens, so the parse tree is complete. The parser accepts the tokens that the lexer produced, and returns a parse tree, so the skeleton of our parse function will look like this: This is because exponentiation is right associative.

They are not prefixes or infixes so it is sufficient to add them to the symbol table.

writing a command line interpreter in java

The evaluator The evaluator accepts the parse tree generated by the parser, evaluates each item, and produces the evaluated output. The skeleton of our evaluate function will look like this.

The parseNode function recursively traverses and evaluates the parse tree.

Some additions would be fairly easy, some could be very hard. Easy stuff Play around with adding your own predefined functions. Fiddle with the binding power numbers to see how that changes the way expressions are evaluated.

Allow scientific notation in number literals or make it possible to use binary or hexidecimal number literals. Intermediate stuff Allow manipulation of more types of data, such as strings, booleans and arrays.

Allow functions to have multiple statements and conditionally return values Replace the evaluator with a compiler or transpiler that takes the parse tree and outputs code in another language Make a package manager that allows you to import code from other files Harder stuff Implement optimizations to allow calculations to be performed more quickly.A lesson on compiling and running a simple program.

Home; Skip to Content; Skip to Search; Oracle. Menu. Sign In Account. Oracle Account. be set using either the -classpath option with the javac compiler command and java interpreter command, The Java interpreter is invoked at the command line on Unix and DOS shell operating .

How to build an interpreter in Java, Part 1: The BASICs BASIC is, quite simply, a basic language. There are two schools of thought on how one might go about writing an interpreter for it.

Essentials, Part 1, Lesson 1: Compiling & Running a Simple Program

One approach is to write a programming loop in which the interpreter program reads one line of text from the interpreted program, parses it, and then. Download source - KB; Writing interpreters and compilers.

Writing an interpreter or a compiler is one of the most educational tasks in programming because you can become familiarized with the details of the code interpretation and evaluation process. Selecting an IDE - The Python interpreter includes a command-line interpreter which can be used in a similar fashion to the Scheme interpreter we saw in class.

However to write stand-alone Python scripts it is convenient to use an IDE that integrates text-editing and running the Python script.

Flags and Arguments

I/O from the Command Line A program is often run from the command line and interacts with the user in the command line environment. The Java platform supports this kind of interaction in two ways: through the Standard Streams and through the Console.

How to write into and read from command line in Java? [duplicate] Ask Question. up vote 1 down vote favorite.

writing a command line interpreter in java

Can you please help me about my situation with a few line of codes or tutorials about both writing and reading commands please? The apache cli package helps you process the command line parameters which were given to your.

Java - Command Line Programs