Table of Contents
vector  Vector data type for Tcl
vector create vecName ?vecName ...? ?switches ?
vector destroy vecName
?vecName ...?
vector expr expression
vector names ?pattern ...?
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.
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 XY 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.
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
= $y(:)"
There are special nonnumeric indices. The index end , specifies
the last component of the vector. It's an error to use this index if the
vector is empty (length is zero). The index ++end can be used to extend
the vector by one component and initialize it to a specific value. You
can't read from the array using this index, though.
# Extend the vector
by one component.
set y(++end) 0.02
The other special indices are min
and max . They return the current smallest and largest components of
the vector.
# Print the bounds of the vector
puts "min=$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 callbacks
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
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"
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 onthefly.
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 nonnumeric
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 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 onecomponent
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 nonzero 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.
 
 Bitwise OR. (Not implemented).
 &&
 Logical AND. Produces a 1 result if both operands are nonzero, 0 otherwise.
 
 Logical OR. Produces a 0 result if both operands are zero, 1 otherwise.
 x?y:z
 Ifthenelse, 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 lefttoright 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 nonnegative 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
32bits are set using the integral portion of the first vector component.
All other components are ignored. The low order 16bits 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 ?
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 index
th 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.
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.
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 callback to be made whenever
the vector is updated or destroyed. By default, the callbacks 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 callback 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 callback. 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
callback 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 callback
routine to be called whenever the vector associated with clientId is
updated or deleted. Proc is a pointer to callback routine and must be
of the type Blt_VectorChangedProc . ClientData is a oneword value to
be passed to the routine when it is invoked. If proc is NULL , then the
client is not notified.
 Results:
 The designated callback 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 callback 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.
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;
}
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.
vector, graph, widget
Table of Contents