Mercurial > ~dholland > hg > ag > index.cgi
diff doc/misc/html/examples/hw.html @ 0:13d2b8934445
Import AnaGram (near-)release tree into Mercurial.
| author | David A. Holland |
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| date | Sat, 22 Dec 2007 17:52:45 -0500 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/doc/misc/html/examples/hw.html Sat Dec 22 17:52:45 2007 -0500 @@ -0,0 +1,155 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"> +<HTML> +<HEAD> +<TITLE>Hello World!</TITLE> +</HEAD> + + +<BODY BGCOLOR="#ffffff" BACKGROUND="tilbl6h.gif" + TEXT="#000000" LINK="#0033CC" + VLINK="#CC0033" ALINK="#CC0099"> + +<P> +<IMG ALIGN="right" SRC="../images/agrsl6c.gif" ALT="AnaGram" + WIDTH=124 HEIGHT=30 > +<BR CLEAR="all"> +Back to <A HREF="../index.html">Index</A> +<P> +<IMG ALIGN="bottom" SRC="../images/rbline6j.gif" ALT="----------------------" + WIDTH=1010 HEIGHT=2 > +<P> + + +<H1>Hello, World!</H1> + +<IMG ALIGN="bottom" SRC="../images/rbline6j.gif" ALT="----------------------" + WIDTH=1010 HEIGHT=2 > + +<P> +<H2>Introduction</H2> +<P> + Hello, world! has become the traditional first program to + try in a new programming language. This directory provides + two instances of "Hello, world!" The first, <tt>hw1</tt>, uses C. The + second, <tt>hw2</tt>, uses C++. +<P> + +<H2>Hello, world! using C - HW1.SYN</H2> + <tt>hw1</tt> accepts a single newline character as input and then + prints the "Hello, world!" message on stdout. +<P> + Every grammar must have a single token, the grammar token, + to which the entire grammar finally condenses. The default + name for this token is "grammar", which is used here. +<P> + AnaGram productions use an arrow ( <CODE>-></CODE> ) to separate the + token or tokens being described, on the left, from their + descriptions, on the right. <tt>hw1</tt> consists of a single + production, defining the token "grammar" to consist of a + single newline character. +<P> + The right hand side of a production is called a "grammar + rule" and in the general case consists of a series of rule + elements separated by commas. Following the rule on the same + line, introduced by an equal sign, there may be a "reduction + procedure", C code to be executed when the rule is + identified in the input stream. Here there is one rule + element and the reduction procedure consists of a single C + expression, followed by a semicolon. +<P> + Note that AnaGram permits comments in accordance with the + rules for C comments. AnaGram comments, like C comments, do + not ordinarily nest. However, you may set the "nest + comments" configuration switch to allow nesting. +<P> + When AnaGram builds a parser, it will provide defaults for + all important aspects of the parser which you do not + specify. In <tt>hw1</tt>, there is no specification of input, so the + parser will be set up to read characters one at a time from + stdin. +<P> + If a syntax file contains no embedded C, AnaGram will + automatically provide a main program to call the parser. + Thus this simple grammar suffices to describe a complete + program. +<P> + +<H2>Testing HW1</H2> + To test <tt>hw1</tt>, run AnaGram and build a parser using + <tt>hw1.syn</tt>. + The name of the output source file will be <tt>hw1.c</tt>. + Compile and link the + parser with your C compiler. Then run it from the command line + and press Enter. + The "Hello, world!" message should appear on your screen. +<P> + +<H2>Hello, world! using C++ - HW2.SYN</H2> + <tt>hw2</tt> is a step up in complexity. <tt>hw2</tt> + creates a C++ program + instead of C, and uses stream I/O to write the famous + message. +<P> + The first complexity is the requirement to tell AnaGram to + output a file with a C++ name rather than a C name. + <!-- + Of + course, this is a frill, since you could probably have + compiled it anyway. + --> + The <b>parser file name</b> configuration + parameter specifies that the name of the parser file should + be the same as the name of the syntax file, but with the + extension <tt>.cpp</tt>. +<P> + The second complexity is the need to provide an #include + statement for <tt>iostream.h</tt> to get a definition of + <tt>cout</tt>. <tt>hw1</tt> + did not need to include <tt>stdio.h</tt>, since the parser + always has + an <CODE>#include</CODE> statement for <tt>stdio.h</tt> to + support the default + input procedures. To provide an <CODE>#include</CODE> + statement, we need a + block of embedded C. +<P> + Since we have a block of embedded C, AnaGram will not create + a main program automatically. So we add a main program which + does nothing but call the parser. The parser name is set (by + default) to <tt>hw2</tt>. +<P> + Note also that in addition to C style comments, AnaGram also + supports C++ style comments. +<P> + +<H2>Testing HW2</H2> + To test <tt>hw2</tt>, build a parser using <tt>hw2.syn</tt>, + just as you did + for <tt>hw1</tt>. This time the name of the parser file will be + <tt>hw2.cpp</tt>. Compile and link the parser with your C++ compiler. + Then run it from the command line and press Enter. The + "Hello, world!" message + should appear on your screen. +</P> + +<BR> +<IMG ALIGN="bottom" SRC="../images/rbline6j.gif" ALT="----------------------" + WIDTH=1010 HEIGHT=2 > +<P> +<IMG ALIGN="right" SRC="../images/pslrb6d.gif" ALT="Parsifal Software" + WIDTH=181 HEIGHT=25> +<BR CLEAR="right"> +<P> +Back to <A HREF="../index.html">Index</A> +<P> +<ADDRESS><FONT SIZE="-1"> + AnaGram parser generator - examples<BR> + Hello World!<BR> + Copyright © 1993-1999, Parsifal Software. <BR> + All Rights Reserved.<BR> +</FONT></ADDRESS> + +</BODY> +</HTML> + +