Syntax design...

This is a discussion on Syntax design... within the A Brief History of Cprogramming.com forums, part of the Community Boards category; Mmm... anyone know what kind of diagram is this? I saw something like this on ORACLE SQL Reference... http://audinue.navhost.com/Draft.jpg Maybe ...

  1. #1
    Ugly C Lover audinue's Avatar
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    Smile Syntax design...

    Mmm... anyone know what kind of diagram is this?
    I saw something like this on ORACLE SQL Reference...

    http://audinue.navhost.com/Draft.jpg

    Maybe I can use it to design a programming language syntax.

    Thanks in advance.

  2. #2
    C++ Witch laserlight's Avatar
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    It is, uh, a syntax diagram. They arguably are an easier to trace alternative to EBNF, but a downside is that they are harder to translate and feed into parser generators.
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    Captain Crash brewbuck's Avatar
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    Quote Originally Posted by laserlight View Post
    It is, uh, a syntax diagram. They arguably are an easier to trace alternative to EBNF, but a downside is that they are harder to translate and feed into parser generators.
    In this case the diagram looks like it was generated by Antlr, so it probably started out in parser form in the first place.
    Code:
    //try
    //{
    	if (a) do { f( b); } while(1);
    	else   do { f(!b); } while(1);
    //}

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    Ugly C Lover audinue's Avatar
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    It is, uh, a syntax diagram. They arguably are an easier to trace alternative to EBNF, but a downside is that they are harder to translate and feed into parser generators.
    Eww.. thanks for the answer laserlight! *_*

    In this case the diagram looks like it was generated by Antlr, so it probably started out in parser form in the first place.
    I drew it myself using Visio, there is a lot of mistake in it since I don't know what Syntax Diagram is.

    Umm... can I add the second silly question?

    We know three types of regular numbers in C...
    Can you tell me what are their name please?

    Code:
    1. 123321, 223311, 1024, 4096
    2. 0x00ff, 0x0123, 0x1212a
    3. 0.1232, 123.121, 0.0001231
    I know the second numbers are known as "hexadecimal numbers"...

    Thank you.

  5. #5
    Cat without Hat CornedBee's Avatar
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    The first are integers in decimal notation.
    The second are integers in hexdecimal notation.
    The third are floating point numbers in point notation.

    There's also integers in octal notation and floating point numbers in scientific notation.
    All the buzzt!
    CornedBee

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  6. #6
    and the Hat of Guessing tabstop's Avatar
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    And in C99, there's also the exciting "floating point numbers in hexadecimal scientific notation".

  7. #7
    Ugly C Lover audinue's Avatar
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    There's also integers in octal notation and floating point numbers in scientific notation.

    And in C99, there's also the exciting "floating point numbers in hexadecimal scientific notation".
    Any example please?

  8. #8
    and the Hat of Guessing tabstop's Avatar
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    You've never seen scientific notation before?
    Anyway, octal always starts with 0, so 037 is octal.
    Scientific notation is what it is: 4.75e128
    And the funky hex stuff uses hex for the significand, but decimal for the exponent, so that same number would look like 0x4.cp128.

  9. #9
    Ugly C Lover audinue's Avatar
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    Oh my god... I never saw those thing.

    o_O... Incredible.

    And yet another silly question...

    I just curious of decimal notation...

    Why we not allowed to start a number from 0?

    For instance: 0000123, 00523

    It will give a clear looks of constants instead of hexadecimal number.

    Code:
    #define ERROR_XXX    00001
    #define ERROR_XXXX   00082
    #define ERROR_XYZ    00103
    #define ERROR_YYY    00127
    Last edited by audinue; 11-16-2008 at 07:39 AM.

  10. #10
    and the Hat of Guessing tabstop's Avatar
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    Because numbers that start with zero are in octal notation.
    Last edited by tabstop; 11-16-2008 at 07:45 AM.

  11. #11
    HelpingYouHelpUsHelpUsAll
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    That "syntax diagram" looks like a failed Railroad Diagram. I would find EBNF easier to understand than those ovals and arrows. whats w/ those arrows anyway, they certainatly don't make it easier to follow.
    Also, I didn't know that numbers that start w/ 0 are in base 8. I am suprised the 0s don't get truncated. Still, in maths (outside of C) 00001 is exactly the same as 1, becasue one has to explicitly define if the number is in a different base to 10 which is default. It works well though as it doesn't limit either number base.
    So something to remember: 0x~ = hex, 0~ = octal, where ~ represents a number
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  12. #12
    C++ Witch laserlight's Avatar
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    Quote Originally Posted by P4R4N01D
    That "syntax diagram" looks like a failed Railroad Diagram. I would find EBNF easier to understand than those ovals and arrows. whats w/ those arrows anyway, they certainatly don't make it easier to follow.
    I believe that "syntax diagram" and "railroad diagram" are synonyms. The arrows allow the reader to distinguish between repetition and alternatives.
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