vector(n) BLT Built-In Commands vector(n)______________________________________________________________________________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 vec‐
tor'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 vec‐
tor 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 analy‐
sis 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 speci‐
fying the index, or the set the entire array by providing a list of
index and value pairs for each element. The disadvantages of associa‐
tive 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 val‐
ues 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 ele‐
ment 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 vec‐
tor 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 com‐
mand. 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 oper‐
ation can be invoked in one of three forms:
vector create vecName
This creates a new vector vecName which initially has no compo‐
nents.
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 repre‐
senting 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 vec‐
tor'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 vec‐
tor. 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 compo‐
nents 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 map‐
ping 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 oper‐
and. 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 com‐
ponent, 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 op‐
erands 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 dis‐
tributed 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 por‐
tion of the first vector component. All other compo‐
nents 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 compo‐
nent and the mean, divided by the length of the vec‐
tor).
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 vec‐
tor 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 argu‐
ment.
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 sup‐
ported:
-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 com‐
pacted after all the indices have been deleted.
vecName dup destName
Copies vecName to destName. DestName is the name of a destina‐
tion vector. If a vector destName already exists, it is over‐
written 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 vec‐
tors.
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 trun‐
cated. 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 vec‐
tor. 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 vec‐
tor.
pending
Returns 1 if a client notification is pending, and 0 oth‐
erwise.
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. Dest‐
Name 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 dis‐
tributed 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 compo‐
nents 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 compo‐
nents 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 vec‐
tors 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 vec‐
tor. 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 vec‐
tor, 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 vec‐
tor 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 dou‐
bles 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 vec‐
tor 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 mes‐
sage.
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 iden‐
tifier, 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 iden‐
tifier 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 vec‐
Name. 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 noti‐
fied.
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 proce‐
dure 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
BLT 2.4 vector(n)
