vector

vector(BLT 2.4)                                                vector(BLT 2.4)



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NAME
       vector -  Vector data type for Tcl

SYNOPSIS
       vector create vecName ?vecName...? ?switches?

       vector destroy vecName ?vecName...?

       vector expr expression

       vector names ?pattern...?
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DESCRIPTION
       The vector command creates a vector of floating point values.  The
       vector's components can be manipulated in three ways: through a Tcl
       array variable, a Tcl command, or the C API.

INTRODUCTION
       A vector is simply an ordered set of numbers.  The components of a
       vector are real numbers, indexed by counting numbers.

       Vectors are common data structures for many applications.  For example,
       a graph may use two vectors to represent the X-Y coordinates of the
       data plotted.  The graph will automatically be redrawn when the vectors
       are updated or changed. By using vectors, you can separate data
       analysis from the graph widget.  This makes it easier, for example, to
       add data transformations, such as splines.  It's possible to plot the
       same data to in multiple graphs, where each graph presents a different
       view or scale of the data.

       You could try to use Tcl's associative arrays as vectors.  Tcl arrays
       are easy to use.  You can access individual elements randomly by
       specifying the index, or the set the entire array by providing a list
       of index and value pairs for each element.  The disadvantages of
       associative arrays as vectors lie in the fact they are implemented as
       hash tables.

       · There's no implied ordering to the associative arrays.  If you used
         vectors for plotting, you would want to insure the second component
         comes after the first, an so on.  This isn't possible since arrays
         are actually hash tables.  For example, you can't get a range of
         values between two indices.  Nor can you sort an array.

       · Arrays consume lots of memory when the number of elements becomes
         large (tens of thousands).  This is because each element's index and
         value are stored as strings in the hash table.

       · The C programming interface is unwieldy.  Normally with vectors, you
         would like to view the Tcl array as you do a C array, as an array of
         floats or doubles.  But with hash tables, you must convert both the
         index and value to and from decimal strings, just to access an
         element in the array.  This makes it cumbersome to perform operations
         on the array as a whole.

       The vector command tries to overcome these disadvantages while still
       retaining the ease of use of Tcl arrays.  The vector command creates
       both a new Tcl command and associate array which are linked to the
       vector components.  You can randomly access vector components though
       the elements of array.  Not have all indices are generated for the
       array, so printing the array (using the parray procedure) does not
       print out all the component values.  You can use the Tcl command to
       access the array as a whole.  You can copy, append, or sort vector
       using its command.  If you need greater performance, or customized
       behavior, you can write your own C code to manage vectors.

EXAMPLE
       You create vectors using the vector command and its create operation.
       # Create a new vector.  vector create y(50) This creates a new vector
       named y.  It has fifty components, by default, initialized to 0.0.  In
       addition, both a Tcl command and array variable, both named y, are
       created.  You can use either the command or variable to query or modify
       components of the vector.  # Set the first value.  set y(0) 9.25 puts
       "y has [y length] components" The array y can be used to read or set
       individual components of the vector.  Vector components are indexed
       from zero.  The array index must be a number less than the number of
       components.  For example, it's an error if you try to set the 51st
       element of y.  # This is an error. The vector only has 50 components.
       set y(50) 0.02 You can also specify a range of indices using a colon
       (:) to separate the first and last indices of the range.  # Set the
       first six components of y set y(0:5) 25.2 If you don't include an
       index, then it will default to the first and/or last component of the
       vector.  # Print out all the components of y puts "y = $y(:)" There are
       special non-numeric indices.  The index end, specifies the last
       component of the vector.  It's an error to use this index if the vector
       is empty (length is zero).  The index ++end can be used to extend the
       vector by one component and initialize it to a specific value.  You
       can't read from the array using this index, though.  # Extend the
       vector by one component.  set y(++end) 0.02 The other special indices
       are min and max.  They return the current smallest and largest
       components of the vector.  # Print the bounds of the vector puts
       "min=$y(min) max=$y(max)" To delete components from a vector, simply
       unset the corresponding array element. In the following example, the
       first component of y is deleted.  All the remaining components of y
       will be moved down by one index as the length of the vector is reduced
       by one.  # Delete the first component unset y(0) puts "new first
       element is $y(0)" The vector's Tcl command can also be used to query or
       set the vector.  # Create and set the components of a new vector vector
       create x x set { 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20 }
       Here we've created a vector x without a initial length specification.
       In this case, the length is zero.  The set operation resets the vector,
       extending it and setting values for each new component.

       There are several operations for vectors.  The range operation lists
       the components of a vector between two indices.  # List the components
       puts "x = [x range 0 end]" You can search for a particular value using
       the search operation.  It returns a list of indices of the components
       with the same value.  If no component has the same value, it returns
       "".  # Find the index of the biggest component set indices [x search
       $x(max)] Other operations copy, append, or sort vectors.  You can
       append vectors or new values onto an existing vector with the append
       operation.  # Append assorted vectors and values to x x append x2 x3 {
       2.3 4.5 } x4 The sort operation sorts the vector.  If any additional
       vectors are specified, they are rearranged in the same order as the
       vector.  For example, you could use it to sort data points represented
       by x and y vectors.  # Sort the data points x sort y The vector x is
       sorted while the components of y are rearranged so that the original
       x,y coordinate pairs are retained.

       The expr operation lets you perform arithmetic on vectors.  The result
       is stored in the vector.  # Add the two vectors and a scalar x expr { x
       + y } x expr { x * 2 } When a vector is modified, resized, or deleted,
       it may trigger call-backs to notify the clients of the vector.  For
       example, when a vector used in the graph widget is updated, the vector
       automatically notifies the widget that it has changed.  The graph can
       then redrawn itself at the next idle point.  By default, the
       notification occurs when Tk is next idle.  This way you can modify the
       vector many times without incurring the penalty of the graph redrawing
       itself for each change.  You can change this behavior using the notify
       operation.  # Make vector x notify after every change x notify always
            ...  # Never notify x notify never      ...  # Force notification
       now x notify now To delete a vector, use the vector delete command.
       Both the vector and its corresponding Tcl command are destroyed.  #
       Remove vector x vector destroy x

SYNTAX
       Vectors are created using the vector create operation.  Th create
       operation can be invoked in one of three forms:

       vector create vecName
              This creates a new vector vecName which initially has no
              components.

       vector create vecName(size)
              This second form creates a new vector which will contain size
              number of components.  The components will be indexed starting
              from zero (0). The default value for the components is 0.0.

       vector create vecName(first:last)
              The last form creates a new vector of indexed first through
              last.  First and last can be any integer value so long as first
              is less than last.

       Vector names must start with a letter and consist of letters, digits,
       or underscores.  # Error: must start with letter vector create 1abc You
       can automatically generate vector names using the "#auto" vector name.
       The create operation will generate a unique vector name.  set vec
       [vector create #auto] puts "$vec has [$vec length] components"

   VECTOR INDICES
       Vectors are indexed by integers.  You can access the individual vector
       components via its array variable or Tcl command.  The string
       representing the index can be an integer, a numeric expression, a
       range, or a special keyword.

       The index must lie within the current range of the vector, otherwise an
       an error message is returned.  Normally the indices of a vector are
       start from 0.  But you can use the offset operation to change a
       vector's indices on-the-fly.  puts $vecName(0) vecName offset -5 puts
       $vecName(-5) You can also use numeric expressions as indices.  The
       result of the expression must be an integer value.  set n 21 set
       vecName($n+3) 50.2 The following special non-numeric indices are
       available: min, max, end, and ++end.  puts "min = $vecName($min)" set
       vecName(end) -1.2 The indices min and max will return the minimum and
       maximum values of the vector.  The index end returns the value of the
       last component in the vector.  The index ++end is used to append new
       value onto the vector.  It automatically extends the vector by one
       component and sets its value.  # Append an new component to the end set
       vecName(++end) 3.2 A range of indices can be indicated by a colon (:).
       # Set the first six components to 1.0 set vecName(0:5) 1.0 If no index
       is supplied the first or last component is assumed.  # Print the values
       of all the components puts $vecName(:)

VECTOR OPERATIONS
       vector create vecName?(size)?... ?switches?
              The create operation creates a new vector vecName.  Both a Tcl
              command and array variable vecName are also created.  The name
              vecName must be unique, so another Tcl command or array variable
              can not already exist in that scope.  You can access the
              components of the vector using its variable.  If you change a
              value in the array, or unset an array element, the vector is
              updated to reflect the changes.  When the variable vecName is
              unset, the vector and its Tcl command are also destroyed.

              The vector has optional switches that affect how the vector is
              created. They are as follows:

              -variable varName
                     Specifies the name of a Tcl variable to be mapped to the
                     vector. If the variable already exists, it is first
                     deleted, then recreated.  If varName is the empty string,
                     then no variable will be mapped.  You can always map a
                     variable back to the vector using the vector's variable
                     operation.

              -command cmdName
                     Maps a Tcl command to the vector. The vector can be
                     accessed using cmdName and one of the vector instance
                     operations.  A Tcl command by that name cannot already
                     exist.  If cmdName is the empty string, no command
                     mapping will be made.

              -watchunset boolean
                     Indicates that the vector should automatically delete
                     itself if the variable associated with the vector is
                     unset.  By default, the vector will not be deleted.  This
                     is different from previous releases.  Set boolean to
                     "true" to get the old behavior.

       vector destroy vecName ?vecName...?

       vector expr expression
              All binary operators take vectors as operands (remember that
              numbers are treated as one-component vectors).  The exact action
              of binary operators depends upon the length of the second
              operand.  If the second operand has only one component, then
              each element of the first vector operand is computed by that
              value.  For example, the expression "x * 2" multiples all
              elements of the vector x by 2.  If the second operand has more
              than one component, both operands must be the same length.  Each
              pair of corresponding elements are computed.  So "x + y" adds
              the the first components of x and y together, the second, and so
              on.

              The valid operators are listed below, grouped in decreasing
              order of precedence:

              -  !                Unary minus and logical NOT.  The unary
                                  minus flips the sign of each component in
                                  the vector.  The logical not operator
                                  returns a vector of whose values are 0.0 or
                                  1.0.  For each non-zero component 1.0 is
                                  returned, 0.0 otherwise.

              ^                   Exponentiation.

              *  /  %             Multiply, divide, remainder.

              +  -                Add and subtract.

              <<  >>              Left and right shift.  Circularly shifts the
                                  values of the vector (not implemented yet).

              <  >  <=  >=        Boolean less, greater, less than or equal,
                                  and greater than or equal.  Each operator
                                  returns a vector of ones and zeros.  If the
                                  condition is true, 1.0 is the component
                                  value, 0.0 otherwise.

              ==  !=              Boolean equal and not equal.  Each operator
                                  returns a vector of ones and zeros.  If the
                                  condition is true, 1.0 is the component
                                  value, 0.0 otherwise.

              |                   Bit-wise OR.  (Not implemented).

              &&                  Logical AND.  Produces a 1 result if both
                                  operands are non-zero, 0 otherwise.

              ||                  Logical OR.  Produces a 0 result if both
                                  operands are zero, 1 otherwise.

              x?y:z               If-then-else, as in C.  (Not implemented
                                  yet).

              See the C manual for more details on the results produced by
              each operator.  All of the binary operators group left-to-right
              within the same precedence level.

              Several mathematical functions are supported for vectors.  Each
              of the following functions invokes the math library function of
              the same name; see the manual entries for the library functions
              for details on what they do.  The operation is applied to all
              elements of the vector returning the results.
              acos        cos         hypot      sinh
              asin        cosh        log        sqrt
              atan        exp         log10      tan
              ceil        floor       sin        tanh Additional functions
              are:

              abs       Returns the absolute value of each component.

              random    Returns a vector of non-negative values uniformly
                        distributed between [0.0, 1.0) using drand48.  The
                        seed comes from the internal clock of the machine or
                        may be set manual with the srandom function.

              round     Rounds each component of the vector.

              srandom   Initializes the random number generator using srand48.
                        The high order 32-bits are set using the integral
                        portion of the first vector component. All other
                        components are ignored.  The low order 16-bits are set
                        to an arbitrary value.

              The following functions return a single value.

              adev      Returns the average deviation (defined as the sum of
                        the absolute values of the differences between
                        component and the mean, divided by the length of the
                        vector).

              kurtosis  Returns the degree of peakedness (fourth moment) of
                        the vector.

              length    Returns the number of components in the vector.

              max       Returns the vector's maximum value.

              mean      Returns the mean value of the vector.

              median    Returns the median of the vector.

              min       Returns the vector's minimum value.

              q1        Returns the first quartile of the vector.

              q3        Returns the third quartile of the vector.

              prod      Returns the product of the components.

              sdev      Returns the standard deviation (defined as the square
                        root of the variance) of the vector.

              skew      Returns the skewness (or third moment) of the vector.
                        This characterizes the degree of asymmetry of the
                        vector about the mean.

              sum       Returns the sum of the components.

              var       Returns the variance of the vector. The sum of the
                        squared differences between each component and the
                        mean is computed.  The variance is the sum divided by
                        the length of the vector minus 1.

              The last set returns a vector of the same length as the
              argument.

              norm      Scales the values of the vector to lie in the range
                        [0.0..1.0].

              sort      Returns the vector components sorted in ascending
                        order.

       vector names ?pattern?

INSTANCE OPERATIONS
       You can also use the vector's Tcl command to query or modify it.  The
       general form is vecName operation ?arg?...  Both operation and its
       arguments determine the exact behavior of the command.  The operations
       available for vectors are listed below.

       vecName append item ?item?...
              Appends the component values from item to vecName.  Item can be
              either the name of a vector or a list of numeric values.

       vecName clear
              Clears the element indices from the array variable associated
              with vecName.  This doesn't affect the components of the vector.
              By default, the number of entries in the Tcl array doesn't match
              the number of components in the vector.  This is because its too
              expensive to maintain decimal strings for both the index and
              value for each component.  Instead, the index and value are
              saved only when you read or write an element with a new index.
              This command removes the index and value strings from the array.
              This is useful when the vector is large.

       vecName delete index ?index?...
              Deletes the indexth component from the vector vecName.  Index is
              the index of the element to be deleted.  This is the same as
              unsetting the array variable element index.  The vector is
              compacted after all the indices have been deleted.

       vecName dup destName
              Copies vecName to destName. DestName is the name of a
              destination vector.  If a vector destName already exists, it is
              overwritten with the components of vecName.  Otherwise a new
              vector is created.

       vecName expr expression
              Computes the expression and resets the values of the vector
              accordingly.  Both scalar and vector math operations are
              allowed.  All values in expressions are either real numbers or
              names of vectors.  All numbers are treated as one component
              vectors.

       vecName length ?newSize?
              Queries or resets the number of components in vecName.  NewSize
              is a number specifying the new size of the vector.  If newSize
              is smaller than the current size of vecName, vecName is
              truncated.  If newSize is greater, the vector is extended and
              the new components are initialized to 0.0.  If no newSize
              argument is present, the current length of the vector is
              returned.

       vecName merge srcName ?srcName?...
              Returns a list of the merged vector components.  The list is
              formed by merging the components of each vector at each index.

       vecName notify keyword
              Controls how vector clients are notified of changes to the
              vector.  The exact behavior is determined by keyword.

              always Indicates that clients are to be notified immediately
                     whenever the vector is updated.

              never  Indicates that no clients are to be notified.

              whenidle
                     Indicates that clients are to be notified at the next
                     idle point whenever the vector is updated.

              now    If any client notifications is currently pending, they
                     are notified immediately.

              cancel Cancels pending notifications of clients using the
                     vector.

              pending
                     Returns 1 if a client notification is pending, and 0
                     otherwise.

       vecName offset ?value?
              Shifts the indices of the vector by the amount specified by
              value.  Value is an integer number.  If no value argument is
              given, the current offset is returned.

       vecName populate destName ?density?
              Creates a vector destName which is a superset of vecName.
              DestName will include all the components of vecName, in addition
              the interval between each of the original components will
              contain a density number of new components, whose values are
              evenly distributed between the original components values.  This
              is useful for generating abscissas to be interpolated along a
              spline.

       vecName range firstIndex ?lastIndex?...
              Returns a list of numeric values representing the vector
              components between two indices. Both firstIndex and lastIndex
              are indices representing the range of components to be returned.
              If lastIndex is less than firstIndex, the components are listed
              in reverse order.

       vecName search value ?value?
              Searches for a value or range of values among the components of
              vecName.  If one value argument is given, a list of indices of
              the components which equal value is returned.  If a second value
              is also provided, then the indices of all components which lie
              within the range of the two values are returned.  If no
              components are found, then "" is returned.

       vecName set item
              Resets the components of the vector to item. Item can be either
              a list of numeric expressions or another vector.

       vecName seq start ?finish? ?step?
              Generates a sequence of values starting with the value start.
              Finish indicates the terminating value of the sequence.  The
              vector is automatically resized to contain just the sequence.
              If three arguments are present, step designates the interval.

              With only two arguments (no finish argument), the sequence will
              continue until the vector is filled.  With one argument, the
              interval defaults to 1.0.

       vecName sort ?-reverse? ?argName?...
              Sorts the vector vecName in increasing order.  If the -reverse
              flag is present, the vector is sorted in decreasing order.  If
              other arguments argName are present, they are the names of
              vectors which will be rearranged in the same manner as vecName.
              Each vector must be the same length as vecName.  You could use
              this to sort the x vector of a graph, while still retaining the
              same x,y coordinate pairs in a y vector.

       vecName variable varName
              Maps a Tcl variable to the vector, creating another means for
              accessing the vector.  The variable varName can't already exist.
              This overrides any current variable mapping the vector may have.

C LANGUAGE API
       You can create, modify, and destroy vectors from C code, using library
       routines.  You need to include the header file blt.h. It contains the
       definition of the structure Blt_Vector, which represents the vector.
       It appears below.  typedef struct {
           double *valueArr;
           int numValues;
           int arraySize;
           double min, max; } Blt_Vector; The field valueArr points to memory
       holding the vector components.  The components are stored in a double
       precision array, whose size size is represented by arraySize.
       NumValues is the length of vector.  The size of the array is always
       equal to or larger than the length of the vector.  Min and max are
       minimum and maximum component values.

LIBRARY ROUTINES
       The following routines are available from C to manage vectors.  Vectors
       are identified by the vector name.

       Blt_CreateVector

         Synopsis:
                   int Blt_CreateVector (interp, vecName, length, vecPtrPtr)
                      Tcl_Interp *interp;
                      char *vecName;
                      int length;
                      Blt_Vector **vecPtrPtr;

         Description:
                   Creates a new vector vecName with a length of length.
                   Blt_CreateVector creates both a new Tcl command and array
                   variable vecName.  Neither a command nor variable named
                   vecName can already exist.  A pointer to the vector is
                   placed into vecPtrPtr.

         Results:  Returns TCL_OK if the vector is successfully created.  If
                   length is negative, a Tcl variable or command vecName
                   already exists, or memory cannot be allocated for the
                   vector, then TCL_ERROR is returned and interp->result will
                   contain an error message.


       Blt_DeleteVectorByName

         Synopsis:
                   int Blt_DeleteVectorByName (interp, vecName)
                      Tcl_Interp *interp;
                      char *vecName;

         Description:
                   Removes the vector vecName.  VecName is the name of a
                   vector which must already exist.  Both the Tcl command and
                   array variable vecName are destroyed.  All clients of the
                   vector will be notified immediately that the vector has
                   been destroyed.

         Results:  Returns TCL_OK if the vector is successfully deleted.  If
                   vecName is not the name a vector, then TCL_ERROR is
                   returned and interp->result will contain an error message.


       Blt_DeleteVector

         Synopsis:
                   int Blt_DeleteVector (vecPtr)
                      Blt_Vector *vecPtr;

         Description:
                   Removes the vector pointed to by vecPtr.  VecPtr is a
                   pointer to a vector, typically set by Blt_GetVector or
                   Blt_CreateVector.  Both the Tcl command and array variable
                   of the vector are destroyed.  All clients of the vector
                   will be notified immediately that the vector has been
                   destroyed.

         Results:  Returns TCL_OK if the vector is successfully deleted.  If
                   vecName is not the name a vector, then TCL_ERROR is
                   returned and interp->result will contain an error message.


       Blt_GetVector

         Synopsis:
                   int Blt_GetVector (interp, vecName, vecPtrPtr)
                      Tcl_Interp *interp;
                      char *vecName;
                      Blt_Vector **vecPtrPtr;

         Description:
                   Retrieves the vector vecName.  VecName is the name of a
                   vector which must already exist.  VecPtrPtr will point be
                   set to the address of the vector.

         Results:  Returns TCL_OK if the vector is successfully retrieved.  If
                   vecName is not the name of a vector, then TCL_ERROR is
                   returned and interp->result will contain an error message.


       Blt_ResetVector

         Synopsis:
                   int Blt_ResetVector (vecPtr, dataArr,
                               numValues, arraySize, freeProc)
                      Blt_Vector *vecPtr;
                      double *dataArr;
                      int *numValues;
                      int *arraySize;
                      Tcl_FreeProc *freeProc;

         Description:
                   Resets the components of the vector pointed to by vecPtr.
                   Calling Blt_ResetVector will trigger the vector to dispatch
                   notifications to its clients. DataArr is the array of
                   doubles which represents the vector data. NumValues is the
                   number of elements in the array. ArraySize is the actual
                   size of the array (the array may be bigger than the number
                   of values stored in it). FreeProc indicates how the storage
                   for the vector component array (dataArr) was allocated.  It
                   is used to determine how to reallocate memory when the
                   vector is resized or destroyed.  It must be TCL_DYNAMIC,
                   TCL_STATIC, TCL_VOLATILE, or a pointer to a function to
                   free the memory allocated for the vector array. If freeProc
                   is TCL_VOLATILE, it indicates that dataArr must be copied
                   and saved.  If freeProc is TCL_DYNAMIC, it indicates that
                   dataArr was dynamically allocated and that Tcl should free
                   dataArr if necessary.  Static indicates that nothing should
                   be done to release storage for dataArr.

         Results:  Returns TCL_OK if the vector is successfully resized.  If
                   newSize is negative, a vector vecName does not exist, or
                   memory cannot be allocated for the vector, then TCL_ERROR
                   is returned and interp->result will contain an error
                   message.


       Blt_ResizeVector

         Synopsis:
                   int Blt_ResizeVector (vecPtr, newSize)
                      Blt_Vector *vecPtr;
                      int newSize;

         Description:
                   Resets the length of the vector pointed to by vecPtr to
                   newSize.  If newSize is smaller than the current size of
                   the vector, it is truncated.  If newSize is greater, the
                   vector is extended and the new components are initialized
                   to 0.0.  Calling Blt_ResetVector will trigger the vector to
                   dispatch notifications.

         Results:  Returns TCL_OK if the vector is successfully resized.  If
                   newSize is negative or memory can not be allocated for the
                   vector, then TCL_ERROR is returned and interp->result will
                   contain an error message.


         Blt_VectorExists

            Synopsis:
                      int Blt_VectorExists (interp, vecName)
                        Tcl_Interp *interp;
                        char *vecName;

            Description:
                      Indicates if a vector named vecName exists in interp.

            Results:  Returns 1 if a vector vecName exists and 0 otherwise.


         If your application needs to be notified when a vector changes, it
         can allocate a unique client identifier for itself.  Using this
         identifier, you can then register a call-back to be made whenever the
         vector is updated or destroyed.  By default, the call-backs are made
         at the next idle point.  This can be changed to occur at the time the
         vector is modified.  An application can allocate more than one
         identifier for any vector.  When the client application is done with
         the vector, it should free the identifier.

         The call-back routine must of the following type.

                typedef void (Blt_VectorChangedProc) (Tcl_Interp *interp,
                   ClientData clientData, Blt_VectorNotify notify);

         ClientData is passed to this routine whenever it is called.  You can
         use this to pass information to the call-back.  The notify argument
         indicates whether the vector has been updated of destroyed. It is an
         enumerated type.

                typedef enum {
                    BLT_VECTOR_NOTIFY_UPDATE=1,
                    BLT_VECTOR_NOTIFY_DESTROY=2
                } Blt_VectorNotify;


         Blt_AllocVectorId

            Synopsis:
                      Blt_VectorId Blt_AllocVectorId (interp, vecName)
                        Tcl_Interp *interp;
                        char *vecName;

            Description:
                      Allocates an client identifier for with the vector
                      vecName.  This identifier can be used to specify a call-
                      back which is triggered when the vector is updated or
                      destroyed.

            Results:  Returns a client identifier if successful.  If vecName
                      is not the name of a vector, then NULL is returned and
                      interp->result will contain an error message.


         Blt_GetVectorById

            Synopsis:
                      int Blt_GetVector (interp, clientId, vecPtrPtr)
                        Tcl_Interp *interp;
                        Blt_VectorId clientId;
                        Blt_Vector **vecPtrPtr;

            Description:
                      Retrieves the vector used by clientId.  ClientId is a
                      valid vector client identifier allocated by
                      Blt_AllocVectorId.  VecPtrPtr will point be set to the
                      address of the vector.

            Results:  Returns TCL_OK if the vector is successfully retrieved.


         Blt_SetVectorChangedProc

            Synopsis:
                      void Blt_SetVectorChangedProc (clientId, proc, clientData);
                        Blt_VectorId clientId;
                        Blt_VectorChangedProc *proc;
                        ClientData *clientData;

            Description:
                      Specifies a call-back routine to be called whenever the
                      vector associated with clientId is updated or deleted.
                      Proc is a pointer to call-back routine and must be of
                      the type Blt_VectorChangedProc.  ClientData is a one-
                      word value to be passed to the routine when it is
                      invoked. If proc is NULL, then the client is not
                      notified.

            Results:  The designated call-back procedure will be invoked when
                      the vector is updated or destroyed.


         Blt_FreeVectorId

            Synopsis:
                      void Blt_FreeVectorId (clientId);
                        Blt_VectorId clientId;

            Description:
                      Frees the client identifier.  Memory allocated for the
                      identifier is released.  The client will no longer be
                      notified when the vector is modified.

            Results:  The designated call-back procedure will be no longer be
                      invoked when the vector is updated or destroyed.


         Blt_NameOfVectorId

            Synopsis:
                      char *Blt_NameOfVectorId (clientId);
                        Blt_VectorId clientId;

            Description:
                      Retrieves the name of the vector associated with the
                      client identifier clientId.

            Results:  Returns the name of the vector associated with clientId.
                      If clientId is not an identifier or the vector has been
                      destroyed, NULL is returned.


         Blt_InstallIndexProc

            Synopsis:
                      void Blt_InstallIndexProc (indexName, procPtr)
                        char *indexName;
                        Blt_VectorIndexProc *procPtr;

            Description:
                      Registers a function to be called to retrieved the index
                      indexName from the vector's array variable.

                      typedef double Blt_VectorIndexProc(Vector *vecPtr);

                      The function will be passed a pointer to the vector.
                      The function must return a double representing the value
                      at the index.

            Results:  The new index is installed into the vector.

C API EXAMPLE
       The following example opens a file of binary data and stores it in an
       array of doubles. The array size is computed from the size of the file.
       If the vector "data" exists, calling Blt_VectorExists, Blt_GetVector is
       called to get the pointer to the vector.  Otherwise the routine
       Blt_CreateVector is called to create a new vector and returns a pointer
       to it. Just like the Tcl interface, both a new Tcl command and array
       variable are created when a new vector is created. It doesn't make any
       difference what the initial size of the vector is since it will be
       reset shortly. The vector is updated when lt_ResetVector is called.
       Blt_ResetVector makes the changes visible to the Tcl interface and
       other vector clients (such as a graph widget).

       #include <tcl.h> #include <blt.h>                    Blt_Vector
       *vecPtr; double *newArr; FILE *f; struct stat statBuf; int numBytes,
       numValues;

       f = fopen("binary.dat", "r"); fstat(fileno(f), &statBuf); numBytes =
       (int)statBuf.st_size;

       /* Allocate an array big enough to hold all the data */ newArr =
       (double *)malloc(numBytes); numValues = numBytes / sizeof(double);
       fread((void *)newArr, numValues, sizeof(double), f); fclose(f);

       if (Blt_VectorExists(interp, "data"))  {
           if (Blt_GetVector(interp, "data", &vecPtr) != TCL_OK) {
                   return TCL_ERROR;
           } } else {
          if (Blt_CreateVector(interp, "data", 0, &vecPtr) != TCL_OK) {
                   return TCL_ERROR;
          } } /*
        * Reset the vector. Clients will be notified when Tk is idle.
        * TCL_DYNAMIC tells the vector to free the memory allocated
        * if it needs to reallocate or destroy the vector.
        */ if (Blt_ResetVector(vecPtr, newArr, numValues, numValues,
                   TCL_DYNAMIC) != TCL_OK) {
           return TCL_ERROR; }

INCOMPATIBILITIES
       In previous versions, if the array variable isn't global (i.e. local to
       a Tcl procedure), the vector is automatically destroyed when the
       procedure returns.  proc doit {} {
           # Temporary vector x
           vector x(10)
           set x(9) 2.0
             ...  }

       This has changed.  Variables are not automatically destroyed when their
       variable is unset.  You can restore the old behavior by setting the
       "-watchunset" switch.

KEYWORDS
       vector, graph, widget



                                                               vector(BLT 2.4)