Procedures

Syntax:

proc name listOfArguments Body

    proc add {x y} {
        expr $x+$y
    }

Semantics:

• Procedures behave just like built-in commands.
• A procedure's return value is return value of last command.
• A value can be explicitly returned with return.
• All variables are local unless specified otherwise.
• The global command is used to declare references to external variables.

Arguments can have defaults:

    proc decr {x {y 1}} {
        expr $x-$y
    }

Variable-length argument lists are declared using args:

    proc sum args {
        set s 0
        foreach i $args {
            set s [expr $s+$i]
        }
        return $s
    }

Examples:

sum 1 2 3 4 5

15

sum

0