Tcl/Tk 2

1
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
• ltcommandgt ltargumentsgt
• set foo bar
• button tw.2.b1 -text "7" ...
• foreach col 1 2 3 4 ...

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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

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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

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Menus

• Use menu to create a menu
• menu tw.menu -tearoff 0
• Use configure -menu to attach a menu to ltwidgetgt
• tw configure -menu tw.menu

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More Menus

• Use add command to add an entry to a menu
• m add command -label "Quit"
  -command Quit

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Binding keys

• The bind command takes 3 arguments
• a widget (where the binding has effect)
• a key sequence
• a command
• bind tw ltControl-Key-qgt "Quit"

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Expression Evaluation

• Expressions are evaluated by invoking the expr
  command
• set len expr foo 3
• Note that square brackets enclose commands

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Control Structures

• foreach (saw earlier)
• if
• switch
• exit

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if

• if condition
• statements
• else
• statements

if x 0 puts stderr "Divide by zero"
else set slope expr y / x
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switch

• switch ltvaluegt
• lttag1gt statements
• lttag2gt statements
• ...
• default statements
• switch foo
• bar set x 0
• baz set x 1

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exit

• exit terminates the application