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>Invoking Happy</TITLE
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><H1
><A
NAME="SEC-INVOKING"
>Chapter 3. Invoking <SPAN
CLASS="APPLICATION"
>Happy</SPAN
></A
></H1
><P
>An invocation of <SPAN
CLASS="APPLICATION"
>Happy</SPAN
> has the following syntax:</P
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><PRE
CLASS="PROGRAMLISTING"
>happy [ <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>options</I
></SPAN
> ] <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>filename</I
></SPAN
> [ <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>options</I
></SPAN
> ]</PRE
></TD
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></TABLE
><P
>All the command line options are optional (!) and may occur
either before or after the input file name.</P
><P
>There are two types of grammar files,
<TT
CLASS="FILENAME"
>file.y</TT
> and <TT
CLASS="FILENAME"
>file.ly</TT
>, with
the latter observing the reverse comment (or literate) convention
(i.e. each code line must begin with the character
<TT
CLASS="LITERAL"
>></TT
>, lines which don't begin with
<TT
CLASS="LITERAL"
>></TT
> are treated as comments). The examples
distributed with <SPAN
CLASS="APPLICATION"
>Happy</SPAN
> are all of the
.ly form.</P
><P
>The flags accepted by <SPAN
CLASS="APPLICATION"
>Happy</SPAN
> are as follows:</P
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><TT
CLASS="LITERAL"
>-a | --arrays</TT
></DT
><DD
><P
> Instructs <SPAN
CLASS="APPLICATION"
>Happy</SPAN
> to generate a parser
using an array-based shift reduce parser. When used in
conjunction with <TT
CLASS="LITERAL"
>-g</TT
>, the arrays will be
encoded as strings, resulting in faster parsers. Without
<TT
CLASS="LITERAL"
>-g</TT
>, standard Haskell arrays will be
used.</P
></DD
><DT
><TT
CLASS="LITERAL"
>-g | --ghc</TT
></DT
><DD
><P
>Instructs <SPAN
CLASS="APPLICATION"
>Happy</SPAN
> to generate a parser
that uses GHC-specific extensions to obtain faster
code.</P
></DD
><DT
><TT
CLASS="LITERAL"
>-c | --coerce</TT
></DT
><DD
><P
> Use GHC's <TT
CLASS="LITERAL"
>unsafeCoerce#</TT
> extension to
generate smaller faster parsers. Type-safety isn't
compromised.</P
><P
>This option may only be used in conjuction with
<TT
CLASS="LITERAL"
>-g</TT
>.</P
></DD
><DT
><TT
CLASS="LITERAL"
>-d | --debug</TT
></DT
><DD
><P
>Generate a parser that will print debugging
information to <TT
CLASS="LITERAL"
>stderr</TT
> at run-time,
including all the shifts, reductions, state transitions and
token inputs performed by the parser.</P
><P
>This option can only be used in conjunction with
<TT
CLASS="LITERAL"
>-a</TT
>.</P
></DD
><DT
><TT
CLASS="LITERAL"
>-i[<filename>] |
--info[=<filename>]</TT
></DT
><DD
><P
> Directs <SPAN
CLASS="APPLICATION"
>Happy</SPAN
> to produce an info file
containing detailed information about the grammar, parser
states, parser actions, and conflicts. Info files are vital
during the debugging of grammars. The filename argument is
optional (note that there's no space between
<TT
CLASS="LITERAL"
>-i</TT
> and the filename in the short
version), and if omitted the info file will be written to
<TT
CLASS="LITERAL"
><file>.info</TT
> (where <TT
CLASS="LITERAL"
><file></TT
>; is
the input file name with any extension removed). </P
></DD
><DT
><TT
CLASS="LITERAL"
>-o <TT
CLASS="REPLACEABLE"
><I
>filename</I
></TT
> |
--outfile=<TT
CLASS="REPLACEABLE"
><I
>filename</I
></TT
></TT
></DT
><DD
><P
>Specifies the destination of the generated parser
module. If omitted, the parser will be placed in
<TT
CLASS="LITERAL"
><TT
CLASS="REPLACEABLE"
><I
>file</I
></TT
>.hs</TT
>, where
<TT
CLASS="REPLACEABLE"
><I
>file</I
></TT
> is the name of the input
file with any extension removed.</P
></DD
><DT
><TT
CLASS="LITERAL"
>-m <TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
> | --magic-name=<TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
></TT
></DT
><DD
><P
> <SPAN
CLASS="APPLICATION"
>Happy</SPAN
> prefixes all the symbols it uses internally
with either <TT
CLASS="LITERAL"
>happy</TT
> or <TT
CLASS="LITERAL"
>Happy</TT
>. To use a
different string, for example if the use of <TT
CLASS="LITERAL"
>happy</TT
>
is conflicting with one of your own functions, specify the
prefix using the <TT
CLASS="LITERAL"
>-m</TT
> option.</P
></DD
><DT
><TT
CLASS="LITERAL"
>-s | --strict</TT
></DT
><DD
><P
>NOTE: the <TT
CLASS="OPTION"
>--strict</TT
> option is
experimental and may cause unpredictable results.</P
><P
>This option causes the right hand side of each
production (the semantic value) to be evaluated eagerly at
the moment the production is reduced. If the lazy behaviour
is not required, then using this option will improve
performance and may reduce space leaks. Note that the
parser as a whole is never lazy - the whole input will
always be consumed before any input is produced, regardless
of the setting of the <TT
CLASS="OPTION"
>--strict</TT
> flag.</P
></DD
><DT
><TT
CLASS="LITERAL"
>-v | --version</TT
></DT
><DD
><P
>Print version information on standard output then exit
successfully.</P
></DD
><DT
><TT
CLASS="LITERAL"
>-t <TT
CLASS="REPLACEABLE"
><I
>directory</I
></TT
> | --template
<TT
CLASS="REPLACEABLE"
><I
>directory</I
></TT
></TT
></DT
><DD
><P
>Instructs <SPAN
CLASS="APPLICATION"
>Happy</SPAN
> to use this directory
when looking for template files: these files contain the
static code that <SPAN
CLASS="APPLICATION"
>Happy</SPAN
> includes in every
generated parser. You shouldn't need to use this option if
<SPAN
CLASS="APPLICATION"
>Happy</SPAN
> is properly configured for your
computer.</P
></DD
></DL
></DIV
><P
> Options that take arguments may be given multiple times, and the
last occurrence will be the value used, except that for
<TT
CLASS="LITERAL"
>--target</TT
>, all the values supplied must be the
same.
</P
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