for loop, multiple checks

This is a discussion on for loop, multiple checks within the C++ Programming forums, part of the General Programming Boards category; Is there a way to shorten this? Code: for(foo == bar || foo == pub) { // Incert drunken code ...

  1. #1
    Registered User
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    for loop, multiple checks

    Is there a way to shorten this?
    Code:
    for(foo == bar || foo == pub)
    {
          // Incert drunken code here
    }
    More specifically, is there a way to as such:
    Code:
    for(foo == bar||pub){}
    Any help would be appreciated

    -Thank You

  2. #2
    and the hat of wrongness Salem's Avatar
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    Nope.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  3. #3
    a_capitalist_story
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    Friends don't let friends code drunk.

  4. #4
    Registered User
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    Code:
    for(foo == bar)
    {
           for(foo == pub)
           {
            }
    break
    }
    errm oh wait thats not shorter

  5. #5
    The larch
    Join Date
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    You might be able to use bit checks:

    Code:
    enum { bar = 1 << 0, pub = 1 << 1 };
    
    while (foo & (bar | pub))
    ...
    I might be wrong.

    Thank you, anon. You sure know how to recognize different types of trees from quite a long way away.
    Quoted more than 1000 times (I hope).

  6. #6
    Master Apprentice phantomotap's Avatar
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    It can be done, it can be approximated, but how much work are you willing to put into making this expression style work?

    I only ask because the code below illustrates about 1/200 of what you'd actually need to cleanly pull off this semantic modification.

    Soma

    Code:
    template
    <
       typename type_F
    >
    struct lhs_type
    {
       lhs_type
       (
          const type_F & value_f
       ):
          value_m(value_f)
       {
       }
       const type_F & value_m;
    };
    
    template
    <
       typename type_F
    >
    lhs_type<type_F> lhs
    (
       const type_F & lhs_f
    )
    {
       return(lhs_type<type_F>(lhs_f));
    }
    
    template
    <
       typename type_F
    >
    struct rhs_type
    {
       rhs_type
       (
          const type_F & value_f
       ):
          value_m(value_f)
       {
       }
       const type_F & value_m;
    };
    
    template
    <
       typename type_F
    >
    rhs_type<type_F> rhs
    (
       const type_F & rhs_f
    )
    {
       return(rhs_type<type_F>(rhs_f));
    }
    
    template
    <
       typename lhs_F,
       typename rhs_F
    >
    struct lor_type
    {
       lor_type
       (
          const lhs_F & lhs_f,
          const rhs_F & rhs_f
       ):
          lhs_m(lhs_f),
          rhs_m(rhs_f)
       {
       }
       const lhs_F & lhs_m;
       const rhs_F & rhs_m;
    };
    
    template
    <
       typename lhs_F,
       typename rhs_F
    >
    lor_type<lhs_F, rhs_F> operator ||
    (
       const lhs_type<lhs_F> & lhs_f,
       const rhs_type<rhs_F> & rhs_f
    )
    {
       return(lor_type<lhs_F, rhs_F>(lhs_f.value_m, rhs_f.value_m));
    }
    
    template
    <
       typename lhs_F,
       typename rhs_lhs_F,
       typename rhs_rhs_F
    >
    bool operator ==
    (
       const lhs_F & lhs_f,
       const lor_type<rhs_lhs_F, rhs_rhs_F> & rhs_f
    )
    {
       return((lhs_f == rhs_f.lhs_m) || (lhs_f == rhs_f.rhs_m));
    }
    
    struct operator_placeholder_type{} operator_placeholder;
    
    template
    <
       typename lhs_F
    >
    lhs_type<lhs_F> operator ||
    (
       const lhs_F & lhs_f,
       const operator_placeholder_type & rhs_f
    )
    {
       return(lhs_type<lhs_F>(lhs_f));
    }
    
    template
    <
       typename lhs_F,
       typename rhs_F
    >
    lor_type<lhs_F, rhs_F> operator ||
    (
       const lhs_type<lhs_F> & lhs_f,
       const rhs_F & rhs_f
    )
    {
       return(lor_type<lhs_F, rhs_F>(lhs_f.value_m, rhs_f));
    }
    
    #include <iostream>
    
    #define my_log_or || operator_placeholder ||
    
    int main()
    {
       if(3 == (lhs(3)||rhs(5)))
       {
          std::cout << '(' << 3 << ':' << 3 << ':' << 5 << ')' << '\n';
       }
       if(4 == (lhs(3)||rhs(5)))
       {
          std::cout << '(' << 4 << ':' << 3 << ':' << 5 << ')' << '\n';
       }
       if(5 == (lhs(3)||rhs(5)))
       {
          std::cout << '(' << 5 << ':' << 3 << ':' << 5 << ')' << '\n';
       }
       if(6 == (6 my_log_or 8))
       {
          std::cout << '(' << 6 << ':' << 6 << ':' << 8 << ')' << '\n';
       }
       if(7 == (6 my_log_or 8))
       {
          std::cout << '(' << 7 << ':' << 6 << ':' << 8 << ')' << '\n';
       }
       if(8 == (6 my_log_or 8))
       {
          std::cout << '(' << 8 << ':' << 6 << ':' << 8 << ')' << '\n';
       }
       return(0);
    }
    Last edited by phantomotap; 02-17-2009 at 04:22 PM. Reason: ^_^

  7. #7
    Captain Crash brewbuck's Avatar
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    Quote Originally Posted by phantomotap View Post
    It can be done, it can be approximated, but how much work are you willing to put into making this expression style work?
    That's reminiscent of Boost::MPL. In fact, if you had access to Boost::MPL, you could slap together something like what the OP is asking in just a few minutes.

    The question is why you'd want to.
    Code:
    //try
    //{
    	if (a) do { f( b); } while(1);
    	else   do { f(!b); } while(1);
    //}

  8. #8
    Master Apprentice phantomotap's Avatar
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    ^_^

    Well, if you had access to 'Boost::Spirit::Phoenix'... you'd mostly be done.

    Soma

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