another pointer question....

This is a discussion on another pointer question.... within the C++ Programming forums, part of the General Programming Boards category; i've got a question... i want to make a REAL small scripting language by using a void * vector. i ...

  1. #1
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    Question another pointer question....

    i've got a question... i want to make a REAL small scripting language by using a void * vector. i would like to know if this code is safe (causing memory leaks maybe?) and if there is any disadvantage for creating variables on the heap only.
    also, i would like to know what you think about it.
    here is my code:
    Code:
    vector<void *> pointers;
    cout<<"Enter a type and a name"<<endl;
    cout<<"Example: int a, string d"<<endl;
    cin.getline(var,100);
    vars=var;
    for(int l=0;l<vars.length();l++){
    if(vars.substr(l,1)==" "){
    pos=l;
    }
    }
    if(type=="int"){
    pointers.push_back(new int);
    cout<<"Value:";cout.flush();
    cin>>(*((int*)pointers[i]));
    cout<<*((int*)pointers[i])<<endl;
    i++;
    }
    
    anyways, thanks for any replay
    Last edited by gftmc; 08-14-2006 at 03:57 AM.

  2. #2
    ZuK
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    Your code doesn't properly parse the input. I assume that this is just some pseudocode.
    Apart from that. If you insert just void pointers into your vector you will loose the type information. You would have to keep the typeinformation in another vector in parallel.
    Since this is supposed to be a scripting language I would suggest some kind of symbol table
    something like this

    Code:
    struct var {
        int type; // possibly an enum
        void * data;
    }
    map<string, var*> symtable;
    this way you could easily lookup the variables via their name.
    A much better solution would be to have a VariableBase class and derive the concrete variable classes from this baseclass and insert pointers to the VariableBase into your symboltable.
    Kurt
    Last edited by ZuK; 08-14-2006 at 04:33 AM.

  3. #3
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    this is just a part of my code. i wanted to post a small, important code, not all the I/O procedure. anyway, thanks for the reply ill try it.

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    Quote Originally Posted by ZuK
    Since this is supposed to be a scripting language I would suggest some kind of symbol table
    something like this

    Code:
    struct var {
        int type; // possibly an enum
        void * data;
    }
    map<string, var*> symtable;
    If the data types aren't too complex, a union of them would be simpler than a void pointer.
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  5. #5
    Cat without Hat CornedBee's Avatar
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    Scrap both void pointers and unions, use a Boost.Variant or Boost.Any.
    All the buzzt!
    CornedBee

    "There is not now, nor has there ever been, nor will there ever be, any programming language in which it is the least bit difficult to write bad code."
    - Flon's Law

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    of course this is possible, but then where is the chalenge? anyway, ill try a union, never realy worked with them before

  7. #7
    Code Goddess Prelude's Avatar
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    >of course this is possible, but then where is the chalenge?
    The challenge is gone, and good riddance. That's the point of abstraction. If you're writing this for yourself and never intend to release it then do what you want. Writing obtuse code for educational purposes is good. But if you're writing it for other people to use then you'd be wise to look for the best solutions, not the most challenging ones.
    My best code is written with the delete key.

  8. #8
    (?<!re)tired Mario F.'s Avatar
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    ... and using boost.any or boost.variant is winning the challenge of good taste
    The programmer’s wife tells him: “Run to the store and pick up a loaf of bread. If they have eggs, get a dozen.”
    The programmer comes home with 12 loaves of bread.


    Originally Posted by brewbuck:
    Reimplementing a large system in another language to get a 25% performance boost is nonsense. It would be cheaper to just get a computer which is 25% faster.

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