error C2106: '=' : left operand must be l-value

This is a discussion on error C2106: '=' : left operand must be l-value within the C Programming forums, part of the General Programming Boards category; Hi, The following code generates the error:"error C2106: '=' : left operand must be l-value" Code: // This is the ...

  1. #1
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    error C2106: '=' : left operand must be l-value

    Hi,

    The following code generates the error:"error C2106: '=' : left operand must be l-value"

    Code:
    // This is the main project file for VC++ application project 
    // generated using an Application Wizard.
    
    #include "stdafx.h"
    #include "stdio.h"
    #using <mscorlib.dll>
    using namespace System;
    
    
    #define IN 1 /* inside a word */
    #define OUT 0 /* outside a word */
    /* count lines, words, and characters in input */
    
    main()
    {
    int c, nl, nw, nc, state;
    state = OUT;
    nl = nw = nc = 0;
    while ((c = getchar()) != EOF) {
    ++nc;
    if (c == '\n')
    ++nl;
    if (c == ' ' || c == '\n' || c = '\t')
    state = OUT;
    else if (state == OUT) {
    state = IN;
    ++nw;
    }
    }
    printf("%d %d %d\n", nl, nw, nc);
    }
    Can you tell me what is the reason?
    Thanks!!

  2. #2
    and the hat of sweating
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    1: Learn to indent your code properly.
    2: Which line is it complaining about, I'm to busy to try to compile it myself.
    3: Should this be == instead of =?
    Code:
    if (c == ' ' || c == '\n' || c = '\t')

  3. #3
    CSharpener vart's Avatar
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    using namespace System;
    is this C?

    you need to indent properly
    and show us the line that caused the error
    also note that c = '\t' should be c == '\t'
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  4. #4
    C++まいる!Cをこわせ! Elysia's Avatar
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    Totally unreadable code. This code will get nowhere. If I'd grate you from A to F, you'd get G.
    http://cpwiki.sourceforge.net/User:Elysia/Indentation
    Last edited by Elysia; 02-06-2008 at 09:42 AM.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  5. #5
    Registered User aLiNuSh's Avatar
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    If you'd give us the line number where the error occurred maybe we could help more...
    Until then there's definitely something wrong here
    Code:
    if (c == ' ' || c == '\n' || c = '\t')
    I'm sure you meant...
    Code:
    if (c == ' ' || c == '\n' || c == '\t')
    I'm not sure if that generated the error, I remember Borland C++ 3.1, which is a very old compiler, used to generate errors like that when assigning values in if statements.

  6. #6
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    Quote Originally Posted by aLiNuSh View Post
    If you'd give us the line number where the error occurred maybe we could help more...
    Until then there's definitely something wrong here
    Code:
    if (c == ' ' || c == '\n' || c = '\t')
    I'm sure you meant...
    Code:
    if (c == ' ' || c == '\n' || c == '\t')
    I'm not sure if that generated the error, I remember Borland C++ 3.1, which is a very old compiler, used to generate errors like that when assigning values in if statements.
    I'm pretty sure that's the problem. (c == ' ' || c == '\n' || c) is not an lvalue (an lvalue is "something that can be assigned a value", so a simple variable, one cell of an array or a dereferences pointer).

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  7. #7
    Frequently Quite Prolix dwks's Avatar
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    And, anyway . . .
    Code:
    if (c == ' ' || c == '\n' || c == '\t')
    Consider isspace() from <ctype.h>. It does basically just that, except more portably. It also counts vertical tabs ('\v') and carriage returns ('\r') as whitespace in the standard C locale, and whatever else might count as "whitespace" in any other locale the user might be using.
    dwk

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    Quote Originally Posted by Elysia View Post
    Totally unreadable code. This code will get nowhere. If I'd grate you from A to F, you'd get G.
    Then you would not make it far as a grader.

  9. #9
    Frequently Quite Prolix dwks's Avatar
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    'G' as in Good!

    If the grading was based purely on indentation, I can't say it would be very favourable, however . . . .
    dwk

    Seek and ye shall find. quaere et invenies.

    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
    "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
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  10. #10
    C++まいる!Cをこわせ! Elysia's Avatar
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    More like G as in garbage.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  11. #11
    Captain Crash brewbuck's Avatar
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    Quote Originally Posted by Elysia View Post
    More like G as in garbage.
    Blah blah blah.

    It takes a lot of experience (years) to completely understand the value of indentation. This is why so many beginners have poor indentation. It's not their fault. Telling a beginner "Remember to indent properly" is just about as memorable as telling somebody "Remember to scratch directly behind your left ear before descending the staircase." It might be important, but without some context it isn't going to stick.

    You can make all sorts of arguments why indentation is important. The beginner will rightfully say, "So what?" This is because of a lack of experience, not stupidity.

    If you want to fail (or, in your case, "worse than fail") introductory students because their indentation sucks, you will find your classes mysteriously empty of students. Nobody wants to learn from a psycho like that.

  12. #12
    C++まいる!Cをこわせ! Elysia's Avatar
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    It amazes me that people even write code with no a single indent at all. How can they even read such code?
    Yes, I'm cranky today.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  13. #13
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    Quote Originally Posted by Elysia View Post
    It amazes me that people even write code with no a single indent at all. How can they even read such code?
    That question assumes they can read even properly indented code. Most beginners deal with a single line at a time.

    Experienced programmers should push the importance of indentation but also remain patient as beginners slowly realize why.

  14. #14
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    > It takes a lot of experience (years) to completely understand the value of indentation. This is why so many
    > beginners have poor indentation. It's not their fault.

    I always indented properly, from the beginning. It was obvious to me that it's hard to get the logic right if one doesn't bother to write the code so it's clear which nesting level one is in.

    > Nobody wants to learn from a psycho like that.

    There are automatic indenting tools available, so even if the student doesn't feel like indenting properly as they go, they can easily take care of it afterwards if they're told how.

  15. #15
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    Quote Originally Posted by robatino View Post
    I always indented properly, from the beginning.
    And some people played the piano at age 2.

    There are automatic indenting tools available, so even if the student doesn't feel like indenting properly as they go, they can easily take care of it afterwards if they're told how.
    Indentation should be taught. I object to the idea of "failing" students for bad indentation at beginning levels. Are we deliberately trying to discourage people from persevering?

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