proc bracess { } {
    set y [set x "def"]
    puts "Remember that set returns the new value of the variable: X: $x Y: $y\n"

    set a "[set x {This is a string within braces within quotes}]"
    puts " x is now $x \n"
    puts " a is now $a \n"

    set b "\\[set y {This is a string within braces within quotes}]"
    # Note the \ escapes the bracket, and must be doubled to be a
    # literal character in double quotes

    puts "Note the \\ escapes the bracket:\n \$b is: $b"
    puts "\$y is: $y"
}

proc expres { } {
    set X 100
    set Y 256
    set Z [expr {$Y + $X}]
    set Z_LABEL "$Y plus $X is "
    # puts "$Z_LABEL $Z"
    # puts "The square root of $Y is [expr "sqrt($Y)"]\n"

    set pi6 [expr {3.1415926/6.0}]
    puts "The sine and cosine of pi/6: [expr {sin($pi6)}] [expr {cos($pi6)}]"

    # Working with arrays

    set a(1) 10
    set a(2) 7
    set a(3) 17
    set b    2
    puts "Sum: [expr {$a(1)+$a($b)}]"

    puts "1/2 is [expr {1/2}]"
    puts "-1/2 is [expr {-1/2}]"
    puts "1./2 is [expr {1./2}]"
    puts "1./3 is [expr {1./3}]"
    puts "d1/3 is [expr {double(1)/3}]"
}

proc example {first {second ""} args} {
    if {$second eq ""} {
        puts "There is only one argument and it is: $first"
        return 1
    } else {
        if {$args eq ""} {
            puts "There are two arguments - $first and $second"
            return 2
        } else {
            puts "There are many arguments - $first and $second and $args"
            return "many"
        }
    }
}

proc SetPositive {variable value } {
    upvar $variable myvar
    if {$value < 0} {
        set myvar [expr {-$value}]
    } else {
        set myvar $value
    }
    return $myvar
}

proc existence {variable} {
    upvar $variable testVar
    if { [info exists testVar] } {
        puts "$variable Exists"
    } else {
        puts "$variable Does Not Exist"
    }
}
proc do_existence { } {
    set x 1
    set y 2
    for {set i 0} {$i < 5} {incr i} {
        set a($i) $i;
    }
    existence x
    unset x
    existence x
}

proc listi { } {
    set x "a b c"
    set y [split 7/4/1776 "/"]
    set z [list puts "arg 2 is $y" ]
    set lst [list "item 1" "item 2" "item 3"]

    puts $x
    puts $y
    puts lst
    puts $lst

    set i 0
    foreach j $x {
        puts "$j is item number $i in list x"
        incr i
    }

    set b [list a b {c d e} {f {g h}}]
    puts "Treated as a list: $b\n"

    set a [concat a b {c d e}           {f {g h}}]
    puts "Concated: $a\n"

    lappend a {ij Klm}
    puts "After lappending: $a\n"

    set b [linsert $a 3 "1 2 3"]
    puts "After linsert at position 3: $b\n"

    set b [lreplace $b 3 5 "AA" "BB"]
    puts "After lreplacing 3 positions with 2 values at position 3: $b\n"
}

proc misterPresidentList { } {
    set list [list {Washington 1789} {Adams 1797} {Jefferson 1801} {Madison 1809} {Monroe 1817} {Adams 1825} ]

    set x [lsearch $list Washington*]
    set y [lsearch $list Madison*]
    incr x
    incr y -1                        ;# Set range to be not-inclusive

    set subsetlist [lrange $list $x $y]

    puts "The following presidents served between Washington and Madison"
    foreach item $subsetlist {
        puts "Starting in [lindex $item 1]: President [lindex $item 0] "
    }

    set x [lsearch $list Madison*]

    set srtlist [lsort $list]
    set y [lsearch $srtlist Madison*]

    puts "\n$x Presidents came before Madison chronologically"
    puts "$y Presidents came before Madison alphabetically"
}

#abc - cba
proc revert { str } {
    set strLength [string length $str]
    set bound [expr {($strLength - 1) / 2 }]
    set strList [split $str ""]

    for { set i 0 } { $i <= $bound } { incr i } {
        set temp [lindex $strList $i]
        lset strList $i [lindex $strList [expr {$strLength - 1 - $i}]]
        lset strList [expr {$strLength - 1 - $i }] $temp
    }
    set str [join $strList ""]
    return $str
}

puts "\n\n\n"
set str "elephant fly slowly"
puts [revert $str]
puts "\n\n\n"