regarding random function

This is a discussion on regarding random function within the C++ Programming forums, part of the General Programming Boards category; i knw that random function random(n) produces random number from 0 to n-1 and through dis i can i easily ...

  1. #1
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    regarding random function

    i knw that random function random(n) produces random number from 0 to n-1 and through dis i can i easily get d random alphabets but if i want to get alphabets in both caps like "AsdRTuhGnK" den how would i break the parameters

    i know to get the large caps the code is

    char ch=random(26)+'A';

    and if i write
    char ch=random(57)+'A'
    then it would give 6 special symbols too
    so is there any solution for it other then to test those six ascii value and to put some alphabets in place of it?

  2. #2
    spurious conceit MK27's Avatar
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    Since A-Z is not contiguous with a-z in the ascii table
    Code:
    int x = rand()%52;  // 0-51
    if (x < 26) x += 'A';
    else x += 'a';
    C programming resources:
    GNU C Function and Macro Index -- glibc reference manual
    The C Book -- nice online learner guide
    Current ISO draft standard
    CCAN -- new CPAN like open source library repository
    3 (different) GNU debugger tutorials: #1 -- #2 -- #3
    cpwiki -- our wiki on sourceforge

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    thnks MK27
    so likewise we can do for string containing numbers and alphabets

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    Quote Originally Posted by MK27 View Post
    Since A-Z is not contiguous with a-z in the ascii table
    Code:
    int x = rand()%52;  // 0-51
    if (x < 26) x += 'A';
    else x += 'a';
    hey there is lil mistake in else x+='a'
    it would be

    else x+=71;

    bcoz when x=26
    then 26+71=97 which is a ascii code for "a"
    but if u add x+='a' then when x=26
    x=26+97=123 which is a ascii code for"{"
    so it would be else x+=71;
    or else x+='G';

  5. #5
    C++ Witch laserlight's Avatar
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    Quote Originally Posted by ratikag
    so likewise we can do for string containing numbers and alphabets
    Speaking of a string, one option is to define a string that contains the possible characters to choose from, then generate a (pseudo)random number that is a valid index of the string, and thus get the corresponding randomly selected character.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  6. #6
    spurious conceit MK27's Avatar
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    Quote Originally Posted by ratikag View Post
    hey there is lil mistake in else x+='a'
    No, there is not if you consider 0-25 to be 'A-Z' and 26-52 to be 'a-z'. If the result is 1, you add 'A' to get "B", if the result is 27 you add 'a' to get "b".

    [edit] Sorry you are right, should've been
    Code:
    else x += 'a'-26;

    Laserlight's idea is a good one esp. if you want to include punctuation, etc.
    Last edited by MK27; 03-05-2010 at 10:09 AM.
    C programming resources:
    GNU C Function and Macro Index -- glibc reference manual
    The C Book -- nice online learner guide
    Current ISO draft standard
    CCAN -- new CPAN like open source library repository
    3 (different) GNU debugger tutorials: #1 -- #2 -- #3
    cpwiki -- our wiki on sourceforge

  7. #7
    Master Apprentice phantomotap's Avatar
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    O_o

    You have a mistake. It isn't a big deal, but your English description doesn't match your source implementation.

    Soma

  8. #8
    spurious conceit MK27's Avatar
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    Quote Originally Posted by phantomotap View Post
    O_o

    You have a mistake.
    Nope -- unless you meant the "and/add" typo which was, contextually, obviously a typo.
    C programming resources:
    GNU C Function and Macro Index -- glibc reference manual
    The C Book -- nice online learner guide
    Current ISO draft standard
    CCAN -- new CPAN like open source library repository
    3 (different) GNU debugger tutorials: #1 -- #2 -- #3
    cpwiki -- our wiki on sourceforge

  9. #9
    Master Apprentice phantomotap's Avatar
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    *shrug*

    I really need to find a new forum...

    Your English description is correct. (I'm not talking about your latest description either.) Your code has a bug. (A bug that was described to you in detail.)

    [Edit]

    I'll just save us both the trouble. Is `original' really producing correct results relating to your goal?

    [/Edit]

    Soma

    Code:
    #include <cstdlib>
    #include <iostream>
    
    char original
    (
    	unsigned int x
    )
    {
    	// unchanged
    	if (x < 26) x += 'A';
    	else x += 'a';
    	return(char(x));
    }
    
    char correct
    (
    	unsigned int value_f
    )
    {
    	if(26 > value_f)
    	{
    		return(char(value_f + 'A'));
    	}
    	else
    	{
    		return(char(value_f + 'a' - 26));
    	}
    }
    
    int main()
    {
    	for(int x(0); 52 > x; ++x)
    	{
    		std::cout << correct(x) << ':' << original(x) << '\n';
    	}
    	return(0);
    }

  10. #10
    spurious conceit MK27's Avatar
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    Quote Originally Posted by phantomotap View Post
    Your code has a bug. (A bug that was described to you in detail.)
    Whoops! It's the idea that counts

    Quote Originally Posted by phantomotap View Post
    I really need to find a new forum...
    Don't be silly -- look how helpful you've been here.
    Last edited by MK27; 03-05-2010 at 10:26 AM.
    C programming resources:
    GNU C Function and Macro Index -- glibc reference manual
    The C Book -- nice online learner guide
    Current ISO draft standard
    CCAN -- new CPAN like open source library repository
    3 (different) GNU debugger tutorials: #1 -- #2 -- #3
    cpwiki -- our wiki on sourceforge

  11. #11
    Master Apprentice phantomotap's Avatar
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    Don't be silly -- look how helpful you've been here.
    O_o

    Then the forum software should stop eating my posts.

    Soma

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