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Import AnaGram (near-)release tree into Mercurial.
author David A. Holland
date Sat, 22 Dec 2007 17:52:45 -0500
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1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
2 <HTML>
3 <HEAD>
4 <TITLE>Hello World!</TITLE>
5 </HEAD>
6
7
8 <BODY BGCOLOR="#ffffff" BACKGROUND="tilbl6h.gif"
9 TEXT="#000000" LINK="#0033CC"
10 VLINK="#CC0033" ALINK="#CC0099">
11
12 <P>
13 <IMG ALIGN="right" SRC="../images/agrsl6c.gif" ALT="AnaGram"
14 WIDTH=124 HEIGHT=30 >
15 <BR CLEAR="all">
16 Back to <A HREF="../index.html">Index</A>
17 <P>
18 <IMG ALIGN="bottom" SRC="../images/rbline6j.gif" ALT="----------------------"
19 WIDTH=1010 HEIGHT=2 >
20 <P>
21
22
23 <H1>Hello, World!</H1>
24
25 <IMG ALIGN="bottom" SRC="../images/rbline6j.gif" ALT="----------------------"
26 WIDTH=1010 HEIGHT=2 >
27
28 <P>
29 <H2>Introduction</H2>
30 <P>
31 Hello, world! has become the traditional first program to
32 try in a new programming language. This directory provides
33 two instances of "Hello, world!" The first, <tt>hw1</tt>, uses C. The
34 second, <tt>hw2</tt>, uses C++.
35 <P>
36
37 <H2>Hello, world! using C &nbsp;&nbsp;-&nbsp;&nbsp; HW1.SYN</H2>
38 <tt>hw1</tt> accepts a single newline character as input and then
39 prints the "Hello, world!" message on stdout.
40 <P>
41 Every grammar must have a single token, the grammar token,
42 to which the entire grammar finally condenses. The default
43 name for this token is "grammar", which is used here.
44 <P>
45 AnaGram productions use an arrow ( <CODE>-&gt;</CODE> ) to separate the
46 token or tokens being described, on the left, from their
47 descriptions, on the right. <tt>hw1</tt> consists of a single
48 production, defining the token "grammar" to consist of a
49 single newline character.
50 <P>
51 The right hand side of a production is called a "grammar
52 rule" and in the general case consists of a series of rule
53 elements separated by commas. Following the rule on the same
54 line, introduced by an equal sign, there may be a "reduction
55 procedure", C code to be executed when the rule is
56 identified in the input stream. Here there is one rule
57 element and the reduction procedure consists of a single C
58 expression, followed by a semicolon.
59 <P>
60 Note that AnaGram permits comments in accordance with the
61 rules for C comments. AnaGram comments, like C comments, do
62 not ordinarily nest. However, you may set the "nest
63 comments" configuration switch to allow nesting.
64 <P>
65 When AnaGram builds a parser, it will provide defaults for
66 all important aspects of the parser which you do not
67 specify. In <tt>hw1</tt>, there is no specification of input, so the
68 parser will be set up to read characters one at a time from
69 stdin.
70 <P>
71 If a syntax file contains no embedded C, AnaGram will
72 automatically provide a main program to call the parser.
73 Thus this simple grammar suffices to describe a complete
74 program.
75 <P>
76
77 <H2>Testing HW1</H2>
78 To test <tt>hw1</tt>, run AnaGram and build a parser using
79 <tt>hw1.syn</tt>.
80 The name of the output source file will be <tt>hw1.c</tt>.
81 Compile and link the
82 parser with your C compiler. Then run it from the command line
83 and press Enter.
84 The "Hello, world!" message should appear on your screen.
85 <P>
86
87 <H2>Hello, world! using C++ &nbsp;&nbsp;-&nbsp;&nbsp; HW2.SYN</H2>
88 <tt>hw2</tt> is a step up in complexity. <tt>hw2</tt>
89 creates a C++ program
90 instead of C, and uses stream I/O to write the famous
91 message.
92 <P>
93 The first complexity is the requirement to tell AnaGram to
94 output a file with a C++ name rather than a C name.
95 <!--
96 Of
97 course, this is a frill, since you could probably have
98 compiled it anyway.
99 -->
100 The <b>parser file name</b> configuration
101 parameter specifies that the name of the parser file should
102 be the same as the name of the syntax file, but with the
103 extension <tt>.cpp</tt>.
104 <P>
105 The second complexity is the need to provide an #include
106 statement for <tt>iostream.h</tt> to get a definition of
107 <tt>cout</tt>. <tt>hw1</tt>
108 did not need to include <tt>stdio.h</tt>, since the parser
109 always has
110 an <CODE>#include</CODE> statement for <tt>stdio.h</tt> to
111 support the default
112 input procedures. To provide an <CODE>#include</CODE>
113 statement, we need a
114 block of embedded C.
115 <P>
116 Since we have a block of embedded C, AnaGram will not create
117 a main program automatically. So we add a main program which
118 does nothing but call the parser. The parser name is set (by
119 default) to <tt>hw2</tt>.
120 <P>
121 Note also that in addition to C style comments, AnaGram also
122 supports C++ style comments.
123 <P>
124
125 <H2>Testing HW2</H2>
126 To test <tt>hw2</tt>, build a parser using <tt>hw2.syn</tt>,
127 just as you did
128 for <tt>hw1</tt>. This time the name of the parser file will be
129 <tt>hw2.cpp</tt>. Compile and link the parser with your C++ compiler.
130 Then run it from the command line and press Enter. The
131 "Hello, world!" message
132 should appear on your screen.
133 </P>
134
135 <BR>
136 <IMG ALIGN="bottom" SRC="../images/rbline6j.gif" ALT="----------------------"
137 WIDTH=1010 HEIGHT=2 >
138 <P>
139 <IMG ALIGN="right" SRC="../images/pslrb6d.gif" ALT="Parsifal Software"
140 WIDTH=181 HEIGHT=25>
141 <BR CLEAR="right">
142 <P>
143 Back to <A HREF="../index.html">Index</A>
144 <P>
145 <ADDRESS><FONT SIZE="-1">
146 AnaGram parser generator - examples<BR>
147 Hello World!<BR>
148 Copyright &copy; 1993-1999, Parsifal Software. <BR>
149 All Rights Reserved.<BR>
150 </FONT></ADDRESS>
151
152 </BODY>
153 </HTML>
154
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