Tcl/Tk 2 CS 414, Software Engineering I Mark Ardis Rose-Hulman Institute December 5, 2002

2 Outline Tcl syntax Menus Key bindings Expression evaluation Control structures

3 Tcl Syntax 1/3 Every Tcl statement begins with a command: set foo $bar button $tw.2.b1 -text "7"... foreach col { }...

4 Tcl Syntax 2/3 Whitespace (spaces or tabs) separates a command from its arguments (and arguments from one another) Newline or semicolon ends a command Use \ to continue a command on another line

5 Tcl Syntax 3/3 Double quotes and curly braces are used to group words together into one argument Quotes allow substitutions to occur Curly braces do not allow substitutions

6 Menus Use menu to create a menu menu $tw.menu -tearoff 0 Use configure -menu to attach a menu to $tw configure -menu $tw.menu

7 More Menus Use add command to add an entry to a menu $m add command -label "Quit" -command Quit

8 Binding keys The bind command takes 3 arguments –a widget (where the binding has effect) –a key sequence –a command bind $tw "Quit"

9 Expression Evaluation Expressions are evaluated by invoking the expr command set len [expr $foo + 3] Note that square brackets enclose commands

10 Control Structures foreach (saw earlier) if switch exit

11 if if {condition} { statements } else { statements } if {$x == 0} { puts stderr "Divide by zero" } else { set slope [expr $y / $x] }

12 switch switch { { statements }... default { statements } } switch $foo { bar { set x 0 } baz { set x 1 } }

13 exit exit terminates the application