gaqworldof.blogg.se - Write a lex program for basic desktop calculator using yacc

Calc/Yylex: lexer specification file in the JLex format.

java files, but there were two special ones: When you called BNFC, you saw it generate lots of files. Putting parser and lexer tools for Java in place However, this will probably not work at first time: you will have to install some more software and set a classpath. If everything goes fine, this will create a parser test class, which you can try out in the following way: If you want to work in Haskell, C, or C++, skip a few sections now.Īssuming you want to work in Java, do the following:

We return to the details of the notation after trying this out in BNFC. The input language is defined with the following BNFC grammar.Ĭopy this code into a file called Calc.cf. To make it the simplest possible, we restrict ourselves to integers, with addition, subtraction, multiplication, and (lossy) division. We start with everyone's favourite: the desktop calculator. Let us now create our first application from a BNFC source file. This means that, after running bnfc, you can create an executable parser by The -m flag makes BNFC to generate a Makefile. The most common choices are:īnfc -m -cpp FILE.cf # to generate C++ with STLīnfc -m -java FILE.cf # to generate Java ≥ 1.5īnfc -m -haskell FILE.cf # to generate Haskell This gives you a list of available options. If you want to contribute to BNFC, make sure you use the latest git version: give the commandīNFC is licensed under the BSD 3-clause license. With GHC in place, just unpack the sources, cd to BNFC, and type make. If you choose the source package, you need the GHC Haskell Compiler. If you are using Debian or Ubuntu Linux, you can obtain BNFC with their package system (but it is a slightly older version).įor the binaries, it is enough to download them and put into a place where you can find executables (such as /usr/local/bin on Unix-like platforms). but some languages have rough corners (e.g.

freedom to change implementation languageīNFC also scales up to legacy programming languages.

automatic documentation (in latex and html).

Strongest case: when designing and implementing a new programming language BNF = Backus-Naur Form (also known as Context-Free Grammars).īNF is the standard format for the specification and documentation of programming languages.īNFC makes BNF usable for implementation as well.īNFC is a high-level front end to traditional implementation formats (in the style of Lex and YACC): "BNFC is a compiler compiler compiler"īNFC saves 90% of source code writing in a typical compiler front end.īNFC can be used for projects carried out in Agda, C, C++, Haskell, Java, OCaml.