Tree implementation, ideas for keyboard input method needed

Discussion in 'C Programming' started by Bubba, Jan 16, 2012.

  1. Bubba

    Bubba Guest

    Greetings,

    nodes of my ordered tree are implemented like this:

    typedef struct __celltype {
    labeltype label;
    struct __celltype *first_child;
    struct __celltype *next_sib;
    struct __celltype *last_child;
    int zadnji;
    } celltype;
    typedef celltype *node;
    typedef celltype *TREE;

    where first_child points to first sibling of the node, next_sib points to
    next sibling and last_child points to last sibling in the node. Data
    zadnji is true if the node is last child of any other node.

    Labeltype is char.

    Here's the whole implementation:

    #include <stdlib.h>
    #include <stdio.h>
    #define LAMBDA NULL
    #define labeltype char

    typedef struct __celltype {
    labeltype label;
    struct __celltype *first_child;
    struct __celltype *next_sib;
    struct __celltype *last_child;
    int zadnji; /*last*/
    } celltype;

    typedef celltype *node;
    typedef celltype *TREE;

    node MAKE_ROOT(labeltype l, TREE *T) {
    if (!(*T = (celltype*) malloc(sizeof(celltype)))) {
    printf("Nema dovoljno memorije.");
    exit(1);
    }
    (*T)->label=l;
    (*T)->first_child=NULL;
    (*T)->next_sib=NULL;
    (*T)->last_child=NULL;
    (*T)->zadnji=0;
    return *T;
    }

    node INSERT_CHILD(labeltype l, node i, TREE *T){
    node temp;
    if (!i) {
    printf("Nema tog cvora.");
    exit(1);
    }
    if (!(i->first_child= (celltype*) malloc(sizeof(celltype)))) {
    printf("Nema dovoljno memorije.");
    exit(1);
    }
    if (i->first_child==NULL) {
    i->first_child->label=l;
    i->first_child->first_child=NULL;
    i->first_child->next_sib=NULL;
    i->first_child->last_child=NULL;
    i->first_child->zadnji=1;
    }
    if (i->first_child!=NULL) {
    temp=i->first_child;
    i->first_child->label=l;
    i->first_child->first_child=NULL;
    i->first_child->next_sib=temp;
    i->first_child->last_child=NULL;
    i->first_child->zadnji=0;
    }
    return i->first_child;
    }

    node ROOT(TREE T){
    return T;
    }

    node INSERT_SIBLING(labeltype l, node i, TREE *T){
    node temp;
    if (!i) {
    printf("Nema tog cvora.");
    exit(1);
    }
    if (!(i->next_sib= (celltype*) malloc(sizeof(celltype)))) {
    printf("Nema dovoljno memorije.");
    exit(1);
    }
    if (i==ROOT(*T)) {
    printf("Taj cvor je korijen.");
    exit(1);
    }
    if(i->zadnji==1){
    i->zadnji=0;
    i->next_sib->label=l;
    i->next_sib->first_child=NULL;
    i->next_sib->next_sib=NULL;
    i->next_sib->last_child=NULL;
    i->next_sib->zadnji=1;
    }
    if(i->zadnji==0){
    temp=i->next_sib;
    i->next_sib->label=l;
    i->next_sib->first_child=NULL;
    i->next_sib->next_sib=temp;
    i->next_sib->last_child=NULL;
    i->next_sib->zadnji=0;
    }
    return i->next_sib;
    }

    node PARENT(node i,TREE T){
    node c, d;
    if (i==ROOT(T)) return LAMBDA;
    if (!i) {
    printf("Nema tog cvora.");
    exit(1);
    }
    for (c=T->first_child; c!=NULL; c=c->next_sib)
    if (c==i) return T;
    for (c=T->first_child; c!=NULL; c=c->next_sib){
    d=PARENT(i,c);
    if (d!=NULL) return d;
    }
    return NULL;
    }

    void DELETE(node i, TREE *T) {
    node c,d,e,f,temp;
    if (i==ROOT(*T)) {
    printf("Taj cvor je korijen."); /*is root*/
    exit(1);
    }
    if (!i) {
    printf("Nema tog cvora."); /*no node*/
    exit(1);
    }
    if (i->first_child!=NULL) {
    printf("Taj cvor ima djece."); /*has sib*/
    exit(1);
    }
    c=PARENT(i,*T);
    if (c->first_child==c->last_child) {
    free(i);
    c->first_child=NULL;
    c->last_child=NULL;
    }
    if (i==c->first_child) {
    temp=i->next_sib;
    free(i);
    c->first_child=temp;
    }
    if(i==c->last_child) {
    d=c->first_child;
    while(d!=c->last_child) {
    if (d->next_sib==i) {
    d->next_sib=NULL;
    d->zadnji=1;
    break;
    }
    d=d->next_sib;
    }
    free(i);
    c->last_child=d;
    }
    if ((i!=c->first_child) && (i!=c->last_child)){

    for (d=c->first_child; d!=NULL; d=d->next_sib){
    if(d->next_sib==i) e=d;
    if(i->next_sib==d) f=d;
    }
    free(i);
    e->next_sib=f;
    }
    }

    node FIRST_CHILD(node i, TREE T){
    if (i->first_child==NULL) return NULL;
    if (!i) {
    printf("Nema tog cvora.");
    exit(1);
    }
    return i->first_child;
    }

    node NEXT_SIBLING(node i, TREE T){
    if (i->next_sib==NULL) return NULL;
    if (!i) {
    printf("Nema tog cvora.");
    exit(1);
    }
    return i->next_sib;
    }

    labeltype LABEL(node i, TREE T) {
    if (!i) {
    printf("Nema tog cvora.");
    exit(1);
    }
    return i->label;
    }

    void CHANGE_LABEL(labeltype l, node i, TREE *T){
    if (!i) {
    printf("Nema tog cvora.");
    exit(1);
    }
    i->label=l;
    }

    void POSTORDER(node i, TREE T) {
    node c;
    for(c=FIRST_CHILD(i,T); c!=LAMBDA; c=NEXT_SIBLING(c,T))
    POSTORDER(c,T);
    printf("%c ", LABEL(i,T));
    }


    int main(void)
    {
    return 0;
    }



    Now I need a sane way to input a tree from keyboard. What would be the
    easiest one?

    Thanks in advance!

    --
    "If you lie to the compiler,
    it will get its revenge."
    Henry Spencer
    2.718281828459045235360287471352662497757247093699959574966967627.com
    Bubba, Jan 16, 2012
    #1
    1. Advertising

  2. Bubba <> writes:

    Just so you know, I'm not going to address your actual question, at
    least for now. I do have some comments on your coding style.

    > nodes of my ordered tree are implemented like this:
    >
    > typedef struct __celltype {
    > labeltype label;
    > struct __celltype *first_child;
    > struct __celltype *next_sib;
    > struct __celltype *last_child;
    > int zadnji;
    > } celltype;


    Identifiers starting with underscores are reserved to the implementation
    in most contexts. Identifiers starting with two underscores are
    reserved in all contexts. You should never define such identifiers
    yourself (unless you're writing code for a C compiler or library
    implementation).

    It's not necessary to use a typedef for a struct type. You could just
    declare it as:

    struct celltype {
    ...
    };

    and simply refer to it as "struct celltype". If you feel the need to
    have a one-word name for the type, there's no need to use different
    identifiers for the tag and typedef:

    typedef struct celltype {
    ...
    } celltype;

    > typedef celltype *node;
    > typedef celltype *TREE;


    Typedefs for pointer types are generally a bad idea. The problem is
    that they hide the fact that the type is a pointer. That's ok if it's a
    truly opaque type, meaning that client code will not use any pointer
    operations on it.

    And logically, a pointer to a "celltype" isn't a node; it points to a node.

    [...]
    > node MAKE_ROOT(labeltype l, TREE *T) {


    All-caps names are conventionally used for macros. It's better style
    to call the function "make_root".

    And in fact I'd declare this as:

    struct celltype *make_root(labeltype label, struct celltype **t);

    Note that "l" is a poor identifier; it's too easily confused with the
    digit "1".

    > if (!(*T = (celltype*) malloc(sizeof(celltype)))) {


    The cast is unnecessary, and could be harmful (in certain circumstances,
    it can inhibit important warnings). malloc() returns a void* result,
    which can be implicitly converted to any pointer type (other than a
    pointer-to-function type).

    A good idiom is:

    if ((*T = malloc(sizeof **T) != NULL) {

    > printf("Nema dovoljno memorije.");


    Error mesages should be printed to stderr and terminated with "\n".

    > exit(1);


    exit(1) doesn't necessarily indicate failure. Use exit(EXIT_FAILURE)
    instead.

    [...]

    --
    Keith Thompson (The_Other_Keith) <http://www.ghoti.net/~kst>
    Will write code for food.
    "We must do something. This is something. Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"
    Keith Thompson, Jan 16, 2012
    #2
    1. Advertising

  3. Bubba <> writes:

    > Greetings,
    >
    > nodes of my ordered tree are implemented like this:
    >
    > typedef struct __celltype {


    __celltype is a reserved name. celltype__ would be fine but then so
    would celltype.

    > labeltype label;
    > struct __celltype *first_child;
    > struct __celltype *next_sib;
    > struct __celltype *last_child;
    > int zadnji;
    > } celltype;
    > typedef celltype *node;
    > typedef celltype *TREE;
    >
    > where first_child points to first sibling of the node, next_sib points to
    > next sibling and last_child points to last sibling in the node. Data
    > zadnji is true if the node is last child of any other node.
    >
    > Labeltype is char.
    >
    > Here's the whole implementation:
    >
    > #include <stdlib.h>
    > #include <stdio.h>
    > #define LAMBDA NULL
    > #define labeltype char
    >
    > typedef struct __celltype {
    > labeltype label;
    > struct __celltype *first_child;
    > struct __celltype *next_sib;
    > struct __celltype *last_child;
    > int zadnji; /*last*/
    > } celltype;
    >
    > typedef celltype *node;
    > typedef celltype *TREE;
    >
    > node MAKE_ROOT(labeltype l, TREE *T) {
    > if (!(*T = (celltype*) malloc(sizeof(celltype)))) {


    What's the cast for? I'd write:

    if ((*T = malloc(sizeof **T)) == NULL)

    That way you know, at first glance, that the size is correct.

    > printf("Nema dovoljno memorije.");
    > exit(1);
    > }


    This code (allocate or fail with a message) is repeated lots of times.
    Is a clear candidate for being a function.

    > (*T)->label=l;
    > (*T)->first_child=NULL;
    > (*T)->next_sib=NULL;
    > (*T)->last_child=NULL;
    > (*T)->zadnji=0;
    > return *T;
    > }
    >
    > node INSERT_CHILD(labeltype l, node i, TREE *T){


    You are using an uncommon naming convention (uppercase function names)
    and unusual layout. Is there are a reason for this?

    > node temp;
    > if (!i) {
    > printf("Nema tog cvora.");
    > exit(1);
    > }
    > if (!(i->first_child= (celltype*) malloc(sizeof(celltype)))) {
    > printf("Nema dovoljno memorije.");
    > exit(1);
    > }
    > if (i->first_child==NULL) {
    > i->first_child->label=l;


    This is obviously wrong. If i->first_child == NULL, you can't talk
    about i->first_child->label.

    > i->first_child->first_child=NULL;
    > i->first_child->next_sib=NULL;
    > i->first_child->last_child=NULL;
    > i->first_child->zadnji=1;
    > }
    > if (i->first_child!=NULL) {


    "else"?

    > temp=i->first_child;
    > i->first_child->label=l;
    > i->first_child->first_child=NULL;
    > i->first_child->next_sib=temp;
    > i->first_child->last_child=NULL;
    > i->first_child->zadnji=0;
    > }
    > return i->first_child;
    > }


    The lack of spaces and the confusion caused by using tabs is making this
    hard to read so I'll stop here.

    <snip code>

    > Now I need a sane way to input a tree from keyboard. What would be the
    > easiest one?


    I'd use parentheses:

    (a b c)
    (a (x (u v) z))

    If you need to indicate "next_sib", use some
    marker character:

    (a b* c)

    --
    Ben.
    Ben Bacarisse, Jan 16, 2012
    #3
  4. Bubba

    Bubba Guest

    Keith Thompson's log on stardate 16 sij 2012

    I hoped for something like this in the first place, so thank you in
    advance!

    > Identifiers starting with underscores are reserved to the
    > implementation in most contexts. Identifiers starting with two
    > underscores are reserved in all contexts. You should never define
    > such identifiers yourself (unless you're writing code for a C
    > compiler or library implementation).


    What are the repercussions of choosing wrong number of underscores? :)

    >> node MAKE_ROOT(labeltype l, TREE *T) {

    >
    > All-caps names are conventionally used for macros. It's better style
    > to call the function "make_root".


    I'm aware of that, thanks, it will be corrected.

    > And in fact I'd declare this as:
    > struct celltype *make_root(labeltype label, struct celltype **t);


    Could you please clarify the need for double pointer?

    > Note that "l" is a poor identifier; it's too easily confused with the
    > digit "1".


    True again!

    >> if (!(*T = (celltype*) malloc(sizeof(celltype)))) {

    > The cast is unnecessary, and could be harmful (in certain
    > circumstances, it can inhibit important warnings). malloc() returns
    > a void* result, which can be implicitly converted to any pointer type
    > (other than a pointer-to-function type).


    I read some posts here about malloc's (non)casting. I'll do as you
    suggested.

    > A good idiom is:
    > if ((*T = malloc(sizeof **T) != NULL) {


    Ok.

    >> printf("Nema dovoljno memorije.");

    > Error mesages should be printed to stderr and terminated with "\n".
    >> exit(1);

    > exit(1) doesn't necessarily indicate failure. Use exit(EXIT_FAILURE)
    > instead.


    Thanks, I'll apply those too!

    --
    "If you lie to the compiler,
    it will get its revenge."
    Henry Spencer
    2.718281828459045235360287471352662497757247093699959574966967627.com
    Bubba, Jan 16, 2012
    #4
  5. Bubba

    Bubba Guest

    Ben Bacarisse's log on stardate 16 sij 2012

    > The lack of spaces and the confusion caused by using tabs is making this
    > hard to read so I'll stop here.


    Wow, this went wrong - I agree; I'll procede as you Keith suggested and
    report back with sorted out code!

    Thanks!

    --
    "If you lie to the compiler,
    it will get its revenge."
    Henry Spencer
    2.718281828459045235360287471352662497757247093699959574966967627.com
    Bubba, Jan 16, 2012
    #5
  6. Bubba

    Kaz Kylheku Guest

    On 2012-01-16, Bubba <> wrote:
    > #define LAMBDA NULL


    While this is a valiant effort, I recommend nothing less than:

    #define PASTE(X, Y) X ## Y
    #define XPASTE(X, Y) PASTE(X, Y)
    #define MKTOKEN(A, B, C, D) XPASTE(XPASTE(A, B), XPASTE(C, D))
    #define LAMBDA MKTOKEN(N, U, L, L)

    Now you've REALLY defined a useless synonym for a useless synonym for zero,
    in style!

    Also, don't foget:

    /* right-associatively-pasted lambda */
    #define R_MKTOKEN(A, B, C, D) XPASTE(A, XPASTE(B, XPASTE(C, D)))
    #define R_LAMBDA R_MKTOKEN(N, U, L, L)

    /* left-associatively-pasted lambda */
    #define L_MKTOKEN(A, B, C, D) XPASTE(XPASTE(XPASTE(A, B), C), D)
    #define L_LAMBDA L_MKTOKEN(N, U, L, L)

    Benchmark all three to see which LAMBDA null pointer constant runs faster!
    Kaz Kylheku, Jan 16, 2012
    #6
  7. Bubba

    Kaz Kylheku Guest

    On 2012-01-16, Bubba <> wrote:
    > Keith Thompson's log on stardate 16 sij 2012
    >
    > I hoped for something like this in the first place, so thank you in
    > advance!
    >
    >> Identifiers starting with underscores are reserved to the
    >> implementation in most contexts. Identifiers starting with two
    >> underscores are reserved in all contexts. You should never define
    >> such identifiers yourself (unless you're writing code for a C
    >> compiler or library implementation).

    >
    > What are the repercussions of choosing wrong number of underscores? :)


    The repercussions are that any of your compiler or library headers are
    completely free to have things like this in them:

    #define __celltype blorch[

    This namespace does not belong to you, but to the implementors.

    (Since C doesn't have namespaces, we have to draw these borders within the
    identifiers themselves.)

    Even if you haven no clash now with __celltype, you could have one tomorrow,
    when you include some header that you did not previously include, port your
    program to a different system, or upgrade (or downgrade) to a different version
    of the compiler or any of your libraries, etc.
    Kaz Kylheku, Jan 16, 2012
    #7
  8. Bubba

    Eric Sosman Guest

    On 1/16/2012 5:01 PM, Bubba wrote:
    > Greetings,
    >
    > nodes of my ordered tree are implemented like this:
    >
    > typedef struct __celltype {


    A minor point: `__celltype' is a reserved identifier, and if
    the implementation decides to use the identifier for its own
    purposes (which it's at liberty to do without warning you), chaos
    is likely to ensue. Use an identifier from the name space belonging
    to the programmer -- `celltype' is fine, yes, even though you're also
    going to use `celltype' as a typedef alias for `struct celltype'.

    > labeltype label;
    > struct __celltype *first_child;
    > struct __celltype *next_sib;
    > struct __celltype *last_child;
    > int zadnji;
    > } celltype;
    > typedef celltype *node;
    > typedef celltype *TREE;


    Another minor point: It's been my experience that typedef aliases
    for pointer types usually cause confusion. "Usually" is not "always,"
    but I think you'd be better off without these aliases. The fact that
    you have two identical aliases suggests that a certain amount of
    confusion may already have crept in: When would you use `node' and
    when would you use `TREE', and what difference are you trying to
    express by choosing one or the other?

    > where first_child points to first sibling of the node, next_sib points to
    > next sibling and last_child points to last sibling in the node.


    I'll assume you mean that `first_child' and `last_child' point
    to the first and last *children* of the node, not to its first and
    last siblings.

    > next sibling and last_child points to last sibling in the node. Data
    > zadnji is true if the node is last child of any other node.
    >
    > Labeltype is char.
    >
    > Here's the whole implementation:
    >
    > #include<stdlib.h>
    > #include<stdio.h>
    > #define LAMBDA NULL
    > #define labeltype char
    >
    > typedef struct __celltype {
    > labeltype label;
    > struct __celltype *first_child;
    > struct __celltype *next_sib;
    > struct __celltype *last_child;
    > int zadnji; /*last*/
    > } celltype;
    >
    > typedef celltype *node;
    > typedef celltype *TREE;
    >
    > node MAKE_ROOT(labeltype l, TREE *T) {
    > if (!(*T = (celltype*) malloc(sizeof(celltype)))) {


    Yet more minor points: First, it's not necessary to cast the
    result of malloc(). Second, the code relies on `TREE' being an
    alias for `celltype*', which means you're not actually getting any
    value out of the `TREE' alias. Here's a better paradigm, no matter
    what type of data `T' points to:

    if (!(*T = malloc(sizeof(**T))) ...

    > printf("Nema dovoljno memorije.");
    > exit(1);


    Minor points: Put a newline '\n' at the end of the message,
    and use exit(EXIT_FAILURE) instead of exit(1).

    As a matter of design, it is usually not a good idea for a
    "low-level" function to make such a drastic decision about the
    fate of the entire program. Normally, it's better to indicate
    failure in some other way, and let the higher-level caller decide
    how to deal with it; the higher-level caller has more "knowledge"
    of the state of the entire program. Even if the eventual action
    is to exit(), the caller might want to do something else first.
    Observe that malloc() does not terminate your program when it
    fails, but instead reports the failure and lets the program make
    its own choice; consider following that pattern in your own code,
    especially in functions near the "leaves."

    > }
    > (*T)->label=l;
    > (*T)->first_child=NULL;
    > (*T)->next_sib=NULL;
    > (*T)->last_child=NULL;
    > (*T)->zadnji=0;
    > return *T;


    Yet another confusion of aliases: This line relies on
    `TREE' being the same as `node'. In one function you've used
    three different names for exactly the same type! Do you think
    this makes the code easier or harder to read?

    There's also a design oddity. The function returns its
    result via two different channels: It stores the new pointer
    at the location pointed to by `T', and it also returns the
    same pointer as the function value. There's nothing actually
    "wrong" with this, but it's unusual enough to raise an eyebrow.
    Usually, you'll want to use just one channel to export a result;
    functions like time() are the exception, not the rule.

    > }
    >
    > node INSERT_CHILD(labeltype l, node i, TREE *T){
    > node temp;
    > if (!i) {
    > printf("Nema tog cvora.");
    > exit(1);
    > }
    > if (!(i->first_child= (celltype*) malloc(sizeof(celltype)))) {
    > printf("Nema dovoljno memorije.");
    > exit(1);
    > }
    > if (i->first_child==NULL) {


    Okay, here's an actual problem: Observe that (1) the code in
    this part of the `if' statement will never execute, and (2) if it
    somehow did execute you'd be trying to store data where the NULL
    pointer points!

    > i->first_child->label=l;
    > i->first_child->first_child=NULL;
    > i->first_child->next_sib=NULL;
    > i->first_child->last_child=NULL;
    > i->first_child->zadnji=1;
    > }
    > if (i->first_child!=NULL) {


    ... and here's another part of the same problem: This code
    will always execute, and will wind up producing an endless loop
    in your data structure: That is, `i->first_child->next_sib' will
    point back to `i->first_child' again. Any siblings that might
    already have existed are now lost forever.

    > temp=i->first_child;
    > i->first_child->label=l;
    > i->first_child->first_child=NULL;
    > i->first_child->next_sib=temp;
    > i->first_child->last_child=NULL;
    > i->first_child->zadnji=0;
    > }
    > return i->first_child;
    > }
    >
    > node ROOT(TREE T){
    > return T;
    > }
    >
    > node INSERT_SIBLING(labeltype l, node i, TREE *T){
    > node temp;
    > if (!i) {
    > printf("Nema tog cvora.");
    > exit(1);
    > }
    > if (!(i->next_sib= (celltype*) malloc(sizeof(celltype)))) {
    > printf("Nema dovoljno memorije.");
    > exit(1);
    > }
    > if (i==ROOT(*T)) {
    > printf("Taj cvor je korijen.");
    > exit(1);
    > }
    > if(i->zadnji==1){
    > i->zadnji=0;
    > i->next_sib->label=l;
    > i->next_sib->first_child=NULL;
    > i->next_sib->next_sib=NULL;
    > i->next_sib->last_child=NULL;
    > i->next_sib->zadnji=1;
    > }
    > if(i->zadnji==0){
    > temp=i->next_sib;
    > i->next_sib->label=l;
    > i->next_sib->first_child=NULL;
    > i->next_sib->next_sib=temp;
    > i->next_sib->last_child=NULL;
    > i->next_sib->zadnji=0;
    > }
    > return i->next_sib;
    > }
    >
    > node PARENT(node i,TREE T){


    If you expect to navigate from child to parent, wouldn't it
    be easier to store that link directly in the node than to do a
    recursive search for it?

    > node c, d;
    > if (i==ROOT(T)) return LAMBDA;
    > if (!i) {
    > printf("Nema tog cvora.");
    > exit(1);
    > }
    > for (c=T->first_child; c!=NULL; c=c->next_sib)
    > if (c==i) return T;
    > for (c=T->first_child; c!=NULL; c=c->next_sib){
    > d=PARENT(i,c);
    > if (d!=NULL) return d;
    > }
    > return NULL;
    > }


    I'm running out of energy, and won't say much more; absence
    of commentary should not be construed as approval! One thing that
    stands out is that you've duplicated the node-building operation
    (allocate memory and initialize the struct) in about five places;
    it would be much simpler (and easier!) to write just one function
    to do this job, and to call it from wherever it's needed. You've
    got three functions whose job is to create a new struct and attach
    it in various ways; consider separating the "create" and "attach"
    operations, and I think you'll have shorter and cleaner code.

    > void DELETE(node i, TREE *T) {
    > node c,d,e,f,temp;
    > if (i==ROOT(*T)) {
    > printf("Taj cvor je korijen."); /*is root*/
    > exit(1);
    > }
    > if (!i) {
    > printf("Nema tog cvora."); /*no node*/
    > exit(1);
    > }
    > if (i->first_child!=NULL) {
    > printf("Taj cvor ima djece."); /*has sib*/
    > exit(1);
    > }
    > c=PARENT(i,*T);
    > if (c->first_child==c->last_child) {
    > free(i);
    > c->first_child=NULL;
    > c->last_child=NULL;
    > }
    > if (i==c->first_child) {
    > temp=i->next_sib;
    > free(i);
    > c->first_child=temp;
    > }
    > if(i==c->last_child) {
    > d=c->first_child;
    > while(d!=c->last_child) {
    > if (d->next_sib==i) {
    > d->next_sib=NULL;
    > d->zadnji=1;
    > break;
    > }
    > d=d->next_sib;
    > }
    > free(i);
    > c->last_child=d;
    > }
    > if ((i!=c->first_child)&& (i!=c->last_child)){
    >
    > for (d=c->first_child; d!=NULL; d=d->next_sib){
    > if(d->next_sib==i) e=d;
    > if(i->next_sib==d) f=d;
    > }
    > free(i);
    > e->next_sib=f;
    > }
    > }
    >
    > node FIRST_CHILD(node i, TREE T){
    > if (i->first_child==NULL) return NULL;
    > if (!i) {
    > printf("Nema tog cvora.");
    > exit(1);
    > }
    > return i->first_child;
    > }
    >
    > node NEXT_SIBLING(node i, TREE T){
    > if (i->next_sib==NULL) return NULL;
    > if (!i) {
    > printf("Nema tog cvora.");
    > exit(1);
    > }
    > return i->next_sib;
    > }
    >
    > labeltype LABEL(node i, TREE T) {
    > if (!i) {
    > printf("Nema tog cvora.");
    > exit(1);
    > }
    > return i->label;
    > }
    >
    > void CHANGE_LABEL(labeltype l, node i, TREE *T){
    > if (!i) {
    > printf("Nema tog cvora.");
    > exit(1);
    > }
    > i->label=l;
    > }
    >
    > void POSTORDER(node i, TREE T) {
    > node c;
    > for(c=FIRST_CHILD(i,T); c!=LAMBDA; c=NEXT_SIBLING(c,T))
    > POSTORDER(c,T);
    > printf("%c ", LABEL(i,T));
    > }
    >
    >
    > int main(void)
    > {
    > return 0;
    > }
    >
    >
    >
    > Now I need a sane way to input a tree from keyboard. What would be the
    > easiest one?


    You could use parentheses to enclose groups of siblings:

    (A(B,C),D,E(F(G,H),I),J)

    could encode a tree that might also be diagrammed as

    A
    +- B
    +- C
    D
    E
    +- F
    +- G
    +- H
    +- I
    J

    But first, fix your code!

    --
    Eric Sosman
    d
    Eric Sosman, Jan 16, 2012
    #8
  9. Keith Thompson <> writes:
    <snip>
    > A good idiom is:
    >
    > if ((*T = malloc(sizeof **T) != NULL) {


    There's a missing ')' of course:

    if ((*T = malloc(sizeof **T)) != NULL) {

    <snip>
    --
    Ben.
    Ben Bacarisse, Jan 16, 2012
    #9
  10. Bubba

    James Kuyper Guest

    On 01/16/2012 05:36 PM, Bubba wrote:
    > Keith Thompson's log on stardate 16 sij 2012
    >
    > I hoped for something like this in the first place, so thank you in
    > advance!
    >
    >> Identifiers starting with underscores are reserved to the
    >> implementation in most contexts. Identifiers starting with two
    >> underscores are reserved in all contexts. You should never define
    >> such identifiers yourself (unless you're writing code for a C
    >> compiler or library implementation).

    >
    > What are the repercussions of choosing wrong number of underscores? :)


    Theoretically: the behavior of your program is undefined. This means
    that the C standard places no restrictions on the behavior of the
    resulting program. That's a bad thing, if there's any particular
    behavior you want your program to have, since it might not have that
    behavior. It's an even worse thing if there are any things your program
    could do that you don't want it to do (such as erasing all of your
    files), because there's a chance that it might do one of those things.

    Practically: identifiers are reserved to the implementation, so they can
    by used by the implementation for it's own purpose, without worrying
    about the possibility that user code might interfere. Consider what
    could go wrong with your program if __celltype is defined by the
    implementation, inside stdlib.h, for some purpose. The best possible
    outcome is that the compiler will notice two different conflicting
    definitions for __celltype, and complain. The worst possibility is that
    __celltype is defined in some way that produces no warning messages when
    you misuse it.

    >> And in fact I'd declare this as:
    >> struct celltype *make_root(labeltype label, struct celltype **t);

    >
    > Could you please clarify the need for double pointer?


    Please don't refer to that as a "double pointer". It's a pointer to a
    pointer. a "double pointer" could be interpreted as referring to a
    "double*".

    I'll let Keith answer the rest of your question in more detail, since
    it's his suggestion.
    --
    James Kuyper
    James Kuyper, Jan 16, 2012
    #10
  11. William Ahern <william@wilbur.25thandClement.com> writes:

    > Ben Bacarisse <> wrote:
    >> Bubba <> writes:

    > <snip>
    >> > temp=i->first_child;
    >> > i->first_child->label=l;
    >> > i->first_child->first_child=NULL;
    >> > i->first_child->next_sib=temp;
    >> > i->first_child->last_child=NULL;
    >> > i->first_child->zadnji=0;
    >> > }
    >> > return i->first_child;
    >> > }

    >
    >> The lack of spaces and the confusion caused by using tabs is making this
    >> hard to read so I'll stop here.

    >
    > You mean confusion caused by *not* using tabs, or by software trying to
    > convert perfectly fine tabs to spaces and--not surprisingly--fscking the
    > indentation?


    By "using" I meant "posting with". Tabs in a post are unlikely to look
    the same as tabs in a code editor. I made the remark when I was looking
    at some code that had tabs, though I see there are some lines that looks
    odd and have no tabs (in the post).

    > Tabs for indentation, spaces for alignment. Almost every editor gets this
    > right by default. It's takes a concerted effort to screw it up. (I'm not
    > laying blame on anyone in particular here. I'm presuming it's the OP's
    > client software that is causing the problem.)


    We are probably in agreement. I don't care what the editor uses for the
    code, but once tabs get into a post, you've almost always lost.

    --
    Ben.
    Ben Bacarisse, Jan 17, 2012
    #11
  12. William Ahern <william@wilbur.25thandClement.com> writes:
    > Ben Bacarisse <> wrote:
    >> Bubba <> writes:

    > <snip>
    >> > temp=i->first_child;
    >> > i->first_child->label=l;
    >> > i->first_child->first_child=NULL;
    >> > i->first_child->next_sib=temp;
    >> > i->first_child->last_child=NULL;
    >> > i->first_child->zadnji=0;
    >> > }
    >> > return i->first_child;
    >> > }

    >
    >> The lack of spaces and the confusion caused by using tabs is making this
    >> hard to read so I'll stop here.

    >
    > You mean confusion caused by *not* using tabs, or by software trying to
    > convert perfectly fine tabs to spaces and--not surprisingly--fscking the
    > indentation?


    No, I'm fairly sure he means confusion caused by using tabs.

    > Tabs for indentation, spaces for alignment. Almost every editor gets this
    > right by default. It's takes a concerted effort to screw it up. (I'm not
    > laying blame on anyone in particular here. I'm presuming it's the OP's
    > client software that is causing the problem.)


    I've worked on far too much code that has a random mixture of tabs
    and spaces, with a tab representing a variable number of columns,
    depending on who modified a particular line of code most recently.
    My personal solution to the problem is to use spaces exclusively
    for indentation -- and that was part of the coding standard at my
    most recent job. (If I worked in environment that required the
    exclusive use of tabs for indentation, of course I'd use tabs.)

    I'm not going to argue that you should follow my convention, but
    you should be aware that there are perfectly legitimate reasons
    for using spaces, even if you don't agree with them; people who use
    spaces rather than tabs aren't necessarily doing so out of ignorance.

    And tabs can cause serious formatting problems when posting to
    Usenet, because there's news software that doesn't handle them
    correctly.

    --
    Keith Thompson (The_Other_Keith) <http://www.ghoti.net/~kst>
    Will write code for food.
    "We must do something. This is something. Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"
    Keith Thompson, Jan 17, 2012
    #12
  13. Bubba <> writes:
    > Keith Thompson's log on stardate 16 sij 2012
    > I hoped for something like this in the first place, so thank you in
    > advance!
    >
    >> Identifiers starting with underscores are reserved to the
    >> implementation in most contexts. Identifiers starting with two
    >> underscores are reserved in all contexts. You should never define
    >> such identifiers yourself (unless you're writing code for a C
    >> compiler or library implementation).

    >
    > What are the repercussions of choosing wrong number of underscores? :)


    Undefined behavior.

    If you're *lucky*, you'll happen to collide with an
    implementation-defined identifier and your code will fail to compile.

    If you're *unlucky*, your program works as you intended it to work, or
    it will fail in subtle ways that are difficult to find.

    The compiler and/or standard runtime library can do anything they like
    with identifiers that start with "__", and nearly anything they like
    with identifiers that start with a single underscore. If you define
    such an identifier yourself, it may or may not conflict with a
    system-defined identifier.

    So don't do that.

    [...]

    >> And in fact I'd declare this as:
    >> struct celltype *make_root(labeltype label, struct celltype **t);

    >
    > Could you please clarify the need for double pointer?


    A "double pointer" could be either a pointer to a pointer, or a pointer
    to type "double". It's better to refer to it as a pointer-to-pointer.

    Why a pointer to a pointer? Don't ask me, it's your code; you declared
    it with a pointer-to-pointer yourself. All I did was replace the
    typedef (which hides the fact that the type is a pointer) with its full
    definition.

    But in general, if you want a function to modify something of type foo,
    you need to pass it a foo*. In this case, "foo" happens to be a pointer
    type itself.

    [...]

    --
    Keith Thompson (The_Other_Keith) <http://www.ghoti.net/~kst>
    Will write code for food.
    "We must do something. This is something. Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"
    Keith Thompson, Jan 17, 2012
    #13
  14. Bubba

    Shao Miller Guest

    On 1/16/2012 18:01, Ben Bacarisse wrote:
    > Keith Thompson<> writes:
    > <snip>
    >> A good idiom is:
    >>
    >> if ((*T = malloc(sizeof **T) != NULL) {

    >
    > There's a missing ')' of course:
    >
    > if ((*T = malloc(sizeof **T)) != NULL) {
    >
    > <snip>


    And change the '!=' to '=='. - Shao
    Shao Miller, Jan 17, 2012
    #14
  15. Shao Miller <> writes:
    > On 1/16/2012 18:01, Ben Bacarisse wrote:
    >> Keith Thompson<> writes:
    >> <snip>
    >>> A good idiom is:
    >>>
    >>> if ((*T = malloc(sizeof **T) != NULL) {

    >>
    >> There's a missing ')' of course:
    >>
    >> if ((*T = malloc(sizeof **T)) != NULL) {
    >>
    >> <snip>

    >
    > And change the '!=' to '=='. - Shao


    Quite right, thanks.

    --
    Keith Thompson (The_Other_Keith) <http://www.ghoti.net/~kst>
    Will write code for food.
    "We must do something. This is something. Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"
    Keith Thompson, Jan 17, 2012
    #15
  16. (Richard Harter) writes:
    > On Mon, 16 Jan 2012 16:35:48 -0800, Keith Thompson <>
    > wrote:

    [...]
    > And if you have a friendly editor it will convert tabs to spaces and
    > vice versa just as you desire.


    But not very well if different past maintainers had different ideas of
    where the tabstops should be. For example, one section of code might
    assume 2-column tabstops, and another might assume 4-column or 8-column
    tabstops.

    Which is ok if tabs (and only tabs) are used exclusively for
    indentation, but not if both sections have a mix of tabs and spaces.

    --
    Keith Thompson (The_Other_Keith) <http://www.ghoti.net/~kst>
    Will write code for food.
    "We must do something. This is something. Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"
    Keith Thompson, Jan 17, 2012
    #16
  17. Bubba

    ImpalerCore Guest

    On Jan 16, 5:01 pm, Bubba <> wrote:
    > Greetings,
    >

    [snip]
    >
    > Now I need a sane way to input a tree from keyboard. What would be the
    > easiest one?
    >
    > Thanks in advance!


    The simplest is probably to leverage an existing XML parser and write
    your own XML format to populate your own custom "DOM" structure. The
    expat and libxml2 are fairly popular, and there are some varying
    implementations of DOM floating around.

    If you want to input a tree from the keyboard, you could type in the
    tree data in XML format, feed it to one of the parsers, and use its
    events to trigger using your interface to populate your tree. It'll
    take some work, but learning how to use an XML parser can be quite
    useful.

    Best regards,
    John D.
    ImpalerCore, Jan 17, 2012
    #17
  18. Bubba

    Kaz Kylheku Guest

    On 2012-01-17, Richard Harter <> wrote:
    > And if you have a friendly editor it will convert tabs to spaces and
    > vice versa just as you desire.


    I use program that I call autotab. This is integrated into
    Vim. When I open a file, autotab is called to analyze up to 5000
    lines of text from the file and emit a configuration for Vim,
    such as whether tabs are expanded with spaces (expandtab), the soft indentation
    size (shiftwidth) and the hard tab size (tabstop).

    The code is here:

    http://www.kylheku.com/cgit/c-snippets/tree/autotab.c

    This program is so rarely wrong that I've stopped fixing the situations when it
    is wrong.
    Kaz Kylheku, Jan 17, 2012
    #18
  19. Bubba

    Eric Sosman Guest

    On 1/16/2012 10:36 PM, ImpalerCore wrote:
    > On Jan 16, 5:01 pm, Bubba<> wrote:
    >> Greetings,
    >>

    > [snip]
    >>
    >> Now I need a sane way to input a tree from keyboard. What would be the
    >> easiest one?
    >>
    >> Thanks in advance!

    >
    > The simplest is probably to leverage an existing XML parser and write
    > your own XML format to populate your own custom "DOM" structure. The
    > expat and libxml2 are fairly popular, and there are some varying
    > implementations of DOM floating around.


    Angels and ministers of grace defend us! The O.P. is trying
    to build a tree in which each node carries a payload of

    ONE

    LONESOME

    `CHAR'

    VALUE

    .... and you want to inflict XML on him?!?!

    Whereabouts do you live, ImpalerCore? I want to be about five
    hundred miles away, and upwind, when you find a cockroach in your
    cupboard and exterminate it with nuclear armaments.

    --
    Eric Sosman
    d
    Eric Sosman, Jan 17, 2012
    #19
  20. (Richard Harter) writes:
    > On Mon, 16 Jan 2012 19:16:10 -0800, Keith Thompson <>
    > wrote:
    >> (Richard Harter) writes:
    >>> On Mon, 16 Jan 2012 16:35:48 -0800, Keith Thompson <>
    >>> wrote:

    >>[...]
    >>> And if you have a friendly editor it will convert tabs to spaces and
    >>> vice versa just as you desire.

    >>
    >>But not very well if different past maintainers had different ideas of
    >>where the tabstops should be. For example, one section of code might
    >>assume 2-column tabstops, and another might assume 4-column or 8-column
    >>tabstops.

    >
    > Within a single file?


    Yes.

    > And your editor displays them all correctly?


    No.

    That was the problem.

    > How remarkable.


    >>Which is ok if tabs (and only tabs) are used exclusively for
    >>indentation, but not if both sections have a mix of tabs and spaces.

    >
    > I don't you caught what I had in mind. If your editor has the option
    > of automatically converting tabs into spaces you can use tabs with the
    > settings you prefer, get the indentation that floats your boat, and
    > still have a tab free file. I keep all of my code in tab free format
    > (except for makefiles - boo, hiss). If your editor can go the other
    > way, i.e., convert those pesky spaces into tabs, you can deal with
    > files that historically have tabs that you want to keep that way.
    > Just convert tabs to spaces, edit, and convert back from spaces to
    > tabs.


    That could work if everyone who modifies the file *either* uses only
    tabs for indentation *or* uses only spaces (with a consistent number
    of columns per level) for indentation. My recent experience does
    not indicate that maintaining that kind of consistency is practical.
    Perhaps in some organizations it would be.

    --
    Keith Thompson (The_Other_Keith) <http://www.ghoti.net/~kst>
    Will write code for food.
    "We must do something. This is something. Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"
    Keith Thompson, Jan 17, 2012
    #20
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. Stub

    B tree, B+ tree and B* tree

    Stub, Nov 12, 2003, in forum: C Programming
    Replies:
    3
    Views:
    10,110
  2. ebrian
    Replies:
    0
    Views:
    326
    ebrian
    Feb 20, 2007
  3. Replies:
    4
    Views:
    668
    Walter Roberson
    Sep 9, 2005
  4. Ryan Macy

    Ideas needed & help needed!

    Ryan Macy, Jul 19, 2006, in forum: Ruby
    Replies:
    2
    Views:
    504
    Ryan Macy
    Jul 19, 2006
  5. Maxi

    Keyboard navigation for TREE Menu

    Maxi, Feb 15, 2006, in forum: Javascript
    Replies:
    0
    Views:
    75
Loading...

Share This Page