📄 sec-tips.html
字号:
<HTML
><HEAD
><TITLE
>Tips</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.74b"><LINK
REL="HOME"
TITLE="Happy User Guide"
HREF="happy.html"><LINK
REL="PREVIOUS"
TITLE="Info Files"
HREF="sec-info-files.html"><LINK
REL="NEXT"
TITLE="Compilation-Time Tips"
HREF="sec-compilation-time.html"></HEAD
><BODY
CLASS="CHAPTER"
><DIV
CLASS="NAVHEADER"
><TABLE
SUMMARY="Header navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="3"
ALIGN="center"
>Happy User Guide</TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="bottom"
><A
HREF="sec-info-files.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="80%"
ALIGN="center"
VALIGN="bottom"
></TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="bottom"
><A
HREF="sec-compilation-time.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="CHAPTER"
><H1
><A
NAME="SEC-TIPS"
>Chapter 6. Tips</A
></H1
><DIV
CLASS="TOC"
><DL
><DT
><B
>Table of Contents</B
></DT
><DT
>6.1. <A
HREF="sec-tips.html#SEC-PERFORMANCE-TIPS"
>Performance Tips</A
></DT
><DT
>6.2. <A
HREF="sec-compilation-time.html"
>Compilation-Time Tips</A
></DT
><DT
>6.3. <A
HREF="sec-finding-errors.html"
>Finding Type Errors</A
></DT
><DT
>6.4. <A
HREF="sec-conflict-tips.html"
>Conflict Tips</A
></DT
><DT
>6.5. <A
HREF="sec-happy-ghci.html"
>Using Happy with <SPAN
CLASS="APPLICATION"
>GHCi</SPAN
></A
></DT
></DL
></DIV
><P
>This section contains a lot of accumulated lore about using
<SPAN
CLASS="APPLICATION"
>Happy</SPAN
>.</P
><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="SEC-PERFORMANCE-TIPS"
>6.1. Performance Tips</A
></H1
><P
>How to make your parser go faster:</P
><P
></P
><UL
><LI
><P
> If you are using GHC, generate parsers using the
<TT
CLASS="LITERAL"
>-a -g -c</TT
> options, and compile them using GHC with
the <TT
CLASS="LITERAL"
>-fglasgow-exts</TT
> option. This is worth a
<SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>lot</I
></SPAN
>, in terms of compile-time,
execution speed and binary size <A
NAME="AEN998"
HREF="#FTN.AEN998"
>[1]</A
>.</P
></LI
><LI
><P
> The lexical analyser is usually the most performance
critical part of a parser, so it's worth spending some time
optimising this. Profiling tools are essential here. In
really dire circumstances, resort to some of the hacks that
are used in the Glasgow Haskell Compiler's interface-file
lexer.</P
></LI
><LI
><P
> Simplify the grammar as much as possible, as this
reduces the number of states and reduction rules that need
to be applied.</P
></LI
><LI
><P
> Use left recursion rather than right recursion
wherever possible. While not strictly a performance issue,
this affects the size of the parser stack, which is kept on
the heap and thus needs to be garbage collected.</P
></LI
></UL
></DIV
></DIV
><H3
CLASS="FOOTNOTES"
>Notes</H3
><TABLE
BORDER="0"
CLASS="FOOTNOTES"
WIDTH="100%"
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
WIDTH="5%"
><A
NAME="FTN.AEN998"
HREF="sec-tips.html#AEN998"
>[1]</A
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
WIDTH="95%"
><P
>omitting the
<TT
CLASS="LITERAL"
>-a</TT
> may generate slightly faster parsers,
but they will be much bigger.</P
></TD
></TR
></TABLE
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="sec-info-files.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="happy.html"
ACCESSKEY="H"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="sec-compilation-time.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>Info Files</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
> </TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>Compilation-Time Tips</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -