vector
Section: BLT BuiltIn Commands (n)
Updated: 2.4
Index
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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...?
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 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.
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 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
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 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 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 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 coshypotsinh
asin coshlogsqrt
atan explog10tan
ceil floorsintanh
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?

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 binread channel ?length? ?switches?

Reads binary values from a Tcl channel. Values are either appended
to the end of the vector or placed at a given index (using the
at option), overwriting existing values. Data is read until EOF
is found on the channel or a specified number of values length
are read (note that this is not necessarily the same as the number of
bytes). The following switches are supported:

 swap

Swap bytes and words. The default endian is the host machine.
 at index

New values will start at vector index index. This will
overwrite any current values.
 format format

Specifies the format of the data. Format can be one of the
following: "i1", "i2", "i4", "i8", "u1, "u2", "u4", "u8", "r4",
"r8", or "r16". The number indicates the number of bytes
required for each value. The letter indicates the type: "i" for signed,
"u" for unsigned, "r" or real. The default format is "r16".
 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?...

Merges the named vectors into a single vector. The resulting
vector is formed by merging the components of each source vector
one index at a time.
 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 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.
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
Index
 NAME

 SYNOPSIS

 DESCRIPTION

 INTRODUCTION

 EXAMPLE

 SYNTAX

 VECTOR INDICES

 VECTOR OPERATIONS

 INSTANCE OPERATIONS

 C LANGUAGE API

 LIBRARY ROUTINES

 C API EXAMPLE

 INCOMPATIBILITIES

 KEYWORDS

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Time: 19:49:25 GMT, April 27, 2011