# The mtr package

## Multiway-branch tree manipulation

###

- ### External abstracts

- ### All abstracts

- ### External functions

- ### All functions

This package provides two layers of functions. Functions of the lower level manipulate multiway-branch trees, implemented according to the classical scheme whereby each node points to its first child and its previous and next siblings. These functions are collected in mtrBasic.c.

Functions of the upper layer deal with group trees, that is the trees used by group sifting to represent the grouping of variables. These functions are collected in mtrGroup.c.

    MtrNode *
    Mtr_AllocNode(

    )

  Allocates new tree node. Returns pointer to node.

  Side Effects None

  See Also `Mtr_DeallocNode`

    MtrNode *
    Mtr_CopyTree(
      MtrNode * node,
      int  expansion
    )

  Makes a copy of tree. If parameter expansion is greater than 1, it will expand the tree by that factor. It is an error for expansion to be less than 1. Returns a pointer to the copy if successful; NULL otherwise.

  Side Effects None

  See Also `Mtr_InitTree`

    MtrNode *
    Mtr_CreateFirstChild(
      MtrNode * parent
    )

  Creates a new node and makes it the first child of parent. Returns pointer to new child.

  Side Effects None

  See Also `Mtr_MakeFirstChild Mtr_CreateLastChild`

    MtrNode *
    Mtr_CreateLastChild(
      MtrNode * parent
    )

  Creates a new node and makes it the last child of parent. Returns pointer to new child.

  Side Effects None

  See Also `Mtr_MakeLastChild Mtr_CreateFirstChild`

    void
    Mtr_DeallocNode(
      MtrNode * node node to be deallocated
    )

  Deallocates tree node.

  Side Effects None

  See Also `Mtr_AllocNode`

    MtrNode *
    Mtr_DissolveGroup(
      MtrNode * group group to be dissolved
    )

  Merges the children of `group' with the children of its parent. Disposes of the node pointed by group. If group is the root of the group tree, this procedure leaves the tree unchanged. Returns the pointer to the parent of `group' upon successful termination; NULL otherwise.

  Side Effects None

  See Also `Mtr_MakeGroup`

    MtrNode *
    Mtr_FindGroup(
      MtrNode * root, root of the group tree
      unsigned int  low, lower bound of the group
      unsigned int  size upper bound of the group
    )

  Finds a group with size leaves starting at low, if it exists. This procedure relies on the low and size fields of each node. It also assumes that the children of each node are sorted in order of increasing low. Returns the pointer to the root of the group upon successful termination; NULL otherwise.

  Side Effects None

    void
    Mtr_FreeTree(
      MtrNode * node
    )

  Disposes of tree rooted at node.

  Side Effects None

  See Also `Mtr_InitTree`

    MtrNode *
    Mtr_InitGroupTree(
      int  lower,
      int  size
    )

  Allocate new tree with one node, whose low and size fields are specified by the lower and size parameters. Returns pointer to tree root.

  Side Effects None

  See Also `Mtr_InitTree Mtr_FreeTree`

    MtrNode *
    Mtr_InitTree(

    )

  Initializes tree with one node. Returns pointer to node.

  Side Effects None

  See Also `Mtr_FreeTree Mtr_InitGroupTree`

    void
    Mtr_MakeFirstChild(
      MtrNode * parent,
      MtrNode * child
    )

  Makes child the first child of parent.

  Side Effects None

  See Also `Mtr_MakeLastChild Mtr_CreateFirstChild`

    MtrNode *
    Mtr_MakeGroup(
      MtrNode * root, root of the group tree
      unsigned int  low, lower bound of the group
      unsigned int  size, upper bound of the group
      unsigned int  flags flags for the new group
    )

  Makes a new group with size leaves starting at low. If the new group intersects an existing group, it must either contain it or be contained by it. This procedure relies on the low and size fields of each node. It also assumes that the children of each node are sorted in order of increasing low. In case of a valid request, the flags of the new group are set to the value passed in `flags.' This can also be used to change the flags of an existing group. Returns the pointer to the root of the new group upon successful termination; NULL otherwise. If the group already exists, the pointer to its root is returned.

  Side Effects None

  See Also `Mtr_DissolveGroup Mtr_ReadGroups Mtr_FindGroup`

    void
    Mtr_MakeLastChild(
      MtrNode * parent,
      MtrNode * child
    )

  Makes child the last child of parent.

  Side Effects None

  See Also `Mtr_MakeFirstChild Mtr_CreateLastChild`

    void
    Mtr_MakeNextSibling(
      MtrNode * first,
      MtrNode * second
    )

  Makes second the next sibling of first. Second becomes a child of the parent of first.

  Side Effects None

    void
    Mtr_PrintGroups(
      MtrNode * root, root of the group tree
      int  silent flag to check tree syntax only
    )

  Prints the groups as a parenthesized list. After each group, the group's flag are printed, preceded by a `|'. For each flag (except MTR_TERMINAL) a character is printed.
  - F: MTR_FIXED
  - N: MTR_NEWNODE
  - S: MTR_SOFT
  The second argument, silent, if different from 0, causes Mtr_PrintGroups to only check the syntax of the group tree.

  Side Effects None

  See Also `Mtr_PrintTree`

    void
    Mtr_PrintTree(
      MtrNode * node
    )

  Prints a tree, one node per line.

  Side Effects None

  See Also `Mtr_PrintGroups`

    MtrNode *
    Mtr_ReadGroups(
      FILE * fp, file pointer
      int  nleaves number of leaves of the new tree
    )

  Reads groups from a file and creates a group tree. Each group is specified by three fields:

       low size flags.

  Low and size are (short) integers. Flags is a string composed of the following characters (with associated translation):
  - D: MTR_DEFAULT
  - F: MTR_FIXED
  - N: MTR_NEWNODE
  - S: MTR_SOFT
  - T: MTR_TERMINAL
  Normally, the only flags that are needed are D and F. Groups and fields are separated by white space (spaces, tabs, and newlines). Returns a pointer to the group tree if successful; NULL otherwise.

  Side Effects None

  See Also `Mtr_InitGroupTree Mtr_MakeGroup`

    int
    Mtr_SwapGroups(
      MtrNode * first, first node to be swapped
      MtrNode * second second node to be swapped
    )

  Swaps two children of a tree node. Adjusts the high and low fields of the two nodes and their descendants. The two children must be adjacent. However, first may be the younger sibling of second. Returns 1 in case of success; 0 otherwise.

  Side Effects None

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