1	Tcl/Tk and Janus Brief introduction 11-753
2	Tcl/Tk Developed by John Ousterhout Tcl = Tool Command Language Scripting language with simple structure Tk is a cross platform widget Tool Kit Part that is responsible for graphical front-end Available also in perl and python Tk has an object oriented look and feel Use only 1 data type: string Designed to allow easy extension (C level)
3	How to start Tcl/Tk Unix: tclsh start tcl wish start tcl+tk janus start tcl+tk+janus janusNX start tcl+janus Important environment variables TCL_LIBRARY, TK_LIBRARY if Tcl/Tk is not installed in the default directory JANUS_LIBRARY, JANUS_LIB, if not compiled by yourself
4	"Tcl basics in 5 minutes" Tcl basics in 5 minutes ~tschaaf/Lectures/11-753/doc/Tcl/Tcl1.html Useful literature and links Brent Welch “Practical Programming in Tcl and Tk” ActiveState Tcl/Tk distribution and code collection http://www.activestate.com/Products/ActiveTcl/ http://aspn.activestate.com/ASPN/Cookbook/Tcl/ Man pages: http://www.tcl.tk/man/ Online Tutorial: http://www.tcl.tk/man/tcl8.5/tutorial/tcltutorial.html
5	Elements of Tcl General structure <command> parameter1 … parameterN ; Command name invokes a internal function that gets the parameters passed Examples set myVar 1 Command “set” creates a variable “myVar” and assigns “1” puts stdout “hello world” Command “puts” writes to stdout the string “hello world” We have to quote the string to make it one parameter
6	Command substitution If a word contains an open bracket (``['') then Tcl performs command substitution. set myVar [expr 1 + 1] To do this it invokes the Tcl interpreter recursively to process the characters following the open bracket as a Tcl script. The script may contain any number of commands and must be terminated by a close bracket (``]''). The result of the script is substituted into the word in place of the brackets. Command substitution is not performed on words enclosed in braces “{}”.
7	Variable substitution If a word contains a $ then Tcl performs variable substitution. Variable substitution may take any of the following forms: $name Name is the name of a scalar variable. $name(index) Name gives the name of an array variable and index gives the name of an element within that array. Command substitutions, variable substitutions, and backslash substitutions are performed on the characters of index. ${name} Name is the name of a scalar variable. It may contain any characters whatsoever except for close braces. There may be any number of variable substitutions in a single word. set myVar $my$Var Variable substitution is not performed on words enclosed in braces set myVar {$my$Var}
8	Order of substitution Each character is processed exactly once by the Tcl interpreter as part of creating the words of a command. For example, if variable substitution occurs then no further substitutions are performed on the value of the variable; the value is inserted into the word verbatim. Substitutions take place from left to right, and each substitution is evaluated completely before attempting to evaluate the next. Thus, a sequence like set y [set x 0][incr x][incr x] will always set the variable y to the value, 012.
9	Common Tcl difficulties set $myVar 10; # this is a valid command if myVar is defined! Sometimes usefull but often a typo. regexp “[ab]c$” $myVar; # it is usually better to quote the regular expresson in “{}”. set x 3 ; set y 2; set myVar [expr $x / $y]; # myVar containes 1 set x 3.0 ; set y 2; set myVar [expr $x / $y]; # myVar containes 1.5 Solution: set x 3 ; set y 2; set myVar [expr $x / double($y)]; # myVar containes 1.5
10	Janus design Janus is integrated in Tcl/Tk All commands from Tcl/Tk available Allows rapid prototyping with a nice GUI Janus is designed object oriented, but implemented in C
11	How to create Janus objects Type class name and instance name FMatrix fm; # create instance fm of class float matrix FeatureSet fs; # create instance fs of class FeatureSet CodebookSet cbs fs; # instance cbs of class CodebookSet that operates on fs cbs add cb1 FEAT 2 10 DIAGONAL; # creates a codebook instance in the set of codebooks cbs with 2 Gaussians of dimension 10 and diagonal covariance which use the feature FEAT stored in fs
12	Getting help <class> and <instance> are names of janus objects % <class> dummy -help List the parameters required to create an instance % <instance> -help List the methods available for this instance % <instance> method –help List the parameters of the methods with default values
13	Access to sub object 2 types of sub objects Sub-objects <instance>.<subobject> Ex. cbs.featureSet Cbs.featureSet –help ;# shows help of featureSet <instance>. List available sub objects Element in set of objects <instance>:<element name> Ex. cbs:cb1 <instance>: ;# list all available elements of set
14	Homework Read Tcl/Tk man pages and play a little Write a Tcl program that saves the first 100 prime numbers into a file. Use arrays.