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83 lines
3.5 KiB
Text
83 lines
3.5 KiB
Text
re2c lesson 001_upn_calculator, (c) M. Boerger 2006
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This lesson gets you started with re2c. In the end you will have an easy RPN
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(reverse polish notation) calculator for use at command line.
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You will learn about the basic interface of re2c when scanning input strings.
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How to detect the end of the input and use that to stop scanning in order to
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avoid problems.
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Once you have successfully installed re2c you can use it to generate *.c files
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from the *.re files presented in this lesson. Actually the expected *.c files
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are already present. So you should name them *.cc or something alike or just
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give them a different name like test.c. To do so you simply change into the
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directory and execute the following command:
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re2c calc_001.re > test.c
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Then use your compiler to compile that code and run it. If you are using gcc
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you simply do the following:
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gcc -o test.o test.c
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./test.o <input_file_name>
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If you are using windows you might want to read till the end of this lesson.
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When you want to debug the code it helps to make re2c generate working #line
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information. To do so you simply specify the output file using the -o switch
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followed by the output filename:
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re2c -o test.c calc_001.re
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The input files *.re each contain basic step by comments that explain what is
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going on and what you can see in the examples.
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In order to optimize the generated code we will use the -s command line switch
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of re2c. This tells re2c to generate code that uses if statements rather
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then endless switch/case expressions where appropriate. Note that the file name
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extension is actually '.s.re' to tell the test system to use the -s switch. To
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invoke re2 you do the following:
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re2c -s -o test.c calc_006.s.re
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Finally we use the -b switch to have the code use a decision table. The -b
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switch also contains the -s behavior.
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re2c -b -o test.c calc_007.b.re
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-------------------------------------------------------------------------------
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For windows users Lynn Allan provided some additional stuff to get you started
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in the Microsoft world. This addon resides in the windows subdirectory and
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gives you something to expereiment with. The code in that directory is based
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on the first step and has the following changes:
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* vc6 .dsp/.dsw and vc7/vc8 .sln/.vcproj project files that have "Custom Build
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Steps" that can tell when main.re changes, and know how to generate main.c
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from main.re. They assume that you unpacked the zip package and have re2c
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itself build or installed in Release and Release-2005 directory respectively.
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If re2c cannot be found you need to modify the custom build step and correct
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the path to re2c.
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* BuildAndRun.bat to do command line rec2 and then cl and then run the
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executable (discontinues with message if errors).
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* built-in cppunit-like test to confirm it worked as expected.
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* array of test strings "fed" to scan rather than file contents to facilitate
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testing and also reduce the newbie learning curve.
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* HiResTimer output for 10,000 loops and 100,000 loops. While this might be
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excessive for this lesson, it illustrates how to do it for subsequent lessons
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and your own stuff using windows. Also it shows that Release build is as fast
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as strncmp for this test and can probably be made significantly faster.
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* If you want to build the other steps of this lesson using windows tools
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simply copy the *.re files into the windows directory as main.re and rebuild.
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-------------------------------------------------------------------------------
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Sidenote: UPN is the german translation of RPN, somehow hardcoded into the
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authors brain :-)
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