📄 sec-grammar-files.html
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>Syntax of Grammar Files</TITLE
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>Chapter 4. Syntax of Grammar Files</A
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>Table of Contents</B
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><DT
>4.1. <A
HREF="sec-grammar-files.html#SEC-LEXICAL-RULES"
>Lexical Rules</A
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>4.3. <A
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>Directives</A
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>4.4. <A
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>Grammar</A
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><P
>The input to <SPAN
CLASS="APPLICATION"
>Happy</SPAN
> is a text file containing
the grammar of the language you want to parse, together with some
annotations that help the parser generator make a legal Haskell
module that can be included in your program. This section gives
the exact syntax of grammar files. </P
><P
>The overall format of the grammar file is given below:</P
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><TD
><PRE
CLASS="PROGRAMLISTING"
><optional module header>
<directives>
%%
<grammar>
<optional module trailer></PRE
></TD
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></TABLE
><P
>If the name of the grammar file ends in <TT
CLASS="LITERAL"
>.ly</TT
>, then
it is assumed to be a literate script. All lines except those
beginning with a <TT
CLASS="LITERAL"
>></TT
> will be ignored, and the
<TT
CLASS="LITERAL"
>></TT
> will be stripped from the beginning of all the code
lines. There must be a blank line between each code section
(lines beginning with <TT
CLASS="LITERAL"
>></TT
>) and comment section.
Grammars not using the literate notation must be in a file with
the <TT
CLASS="LITERAL"
>.y</TT
> suffix.</P
><DIV
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><H1
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><A
NAME="SEC-LEXICAL-RULES"
>4.1. Lexical Rules</A
></H1
><P
>Identifiers in <SPAN
CLASS="APPLICATION"
>Happy</SPAN
> grammar files must take the following form (using
the BNF syntax from the Haskell Report):</P
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> id ::= alpha { idchar }
| ' { any{^'} | \' } '
| " { any{^"} | \" } "
alpha ::= A | B | ... | Z
| a | b | ... | z
idchar ::= alpha
| 0 | 1 | ... | 9
| _</PRE
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