#! /bin/env tclsh

# See Wikit page [Exec Magic] for an explanation of the above.

# Added 2 Jun 01-- Program information.
# Comments are generally good, especially when someone might look 
# at your code and wonder what you were smoking/thinking when you 
# wrote that.

# This is called vector.tcl, and takes two arguments. Each argument
# is a comma divided set of 3 numbers, in the form of 12,34,56.
# It does some error checking, and then calculates the angle of
# difference between the pair of coordinated, and calls that the
# vector. Finally, it figures the distance between the two coordinates.

# Output looks like:
# $ ./vector.tcl 12,23,34 54,43,32
# To get from 12,23,34 to 54,43,32 you vector 42,20,-2 for 46.5617869073
# The plan, and I do have one, is to make this modular, and then put
# it into Tk. This is just one part of the Space Game.


# Check for the right number of arguments, and have at least one error
# message.

set errorMsg "Please use the right number of arguments and coordinates\
    in the form of:
    $argv0 aa,bb,cc xx,yy,zz"

if { $argc != 2 } {
    puts $errorMsg
    exit
}

# This gave a more detailed error message.
proc coordError { badCoord } {
    puts "$badCoord is not a valid coordinate in this universe."
    exit
}

# I'm rather fond of this one, it took me hours to figure out.
# The first version had a second argument of the variable name
# that was to be used. However, I could not get it to work. This
# one does two tests for the if, and then returns the proper 
# list of 3 numbers if everything is right.
proc validateCoord { coord } {
    set coordName [ split $coord , ]
    if {([ llength $coordName ] != "3") || \
        ([regexp -- {[^0-9 ]}  "$coordName"])} {

        # The more detailed error message
        coordError $coord
    }
    return $coordName
}

set hereNow [ lindex $argv 0  ]
set thereThen [ lindex $argv 1 ]

set hereCoord [ validateCoord $hereNow ]
set thereCoord [ validateCoord $thereThen ]

# Foreach #1
# here is the first improvement, it replaces the while loop below:
# '''why replace the other loop?  What makes this better?'''
foreach x1 $hereCoord x2 $thereCoord {
    lappend vector [expr {$x2 - $x1}]
}

# This replaced by Foreach #1
#set labelCoord  [ list X Y Z ]
#set counter 0
#while { $counter < [ llength $hereCoord ] } {
#       set v [ lindex $labelCoord $counter ]
#       set vector$v [ expr [ lindex $hereCoord $counter ] \
#               - [ lindex $thereCoord $counter ] ]
##       set type vector
#       set V [ expr [ lindex $hereCoord $counter ] \
#               - [ lindex $thereCoord $counter ] ]
#        set sqrAbsVector${v} [ expr abs($V) * abs($V) ]
#       incr counter
#}

# These were early drops, though they go the script working.
# Such repetitive lines should be automated.
#set sqrAbsVectorX [ expr abs($vectorX) * abs($vectorX) ]
#set sqrAbsVectorY [ expr abs($vectorY) * abs($vectorY) ]
#set sqrAbsVectorZ [ expr abs($vectorZ) * abs($vectorZ) ]

# Foreach #2, to replace the distance math.
# I had to read up on foreach to get this.
# '''what is this foreach doing?'''
foreach {X Y Z} $vector  break 

# It was giving me errors about vector, so a temporary "puts"
#puts " After: $vector "

#The first set was given to better do the math, however, it had an
# error-- the sqrAbs${vector} would set the variable to:
#  "sqrAbs-11 -22 9"
#set sqrAbs${vector} [expr {hypot($X, [expr hypot($Y,$Z)])}]
set distance [expr {hypot($X, hypot($Y,$Z))}]
# {end of Foreach #2}

# Replaced by Foreach #2
#set distance [ expr sqrt($sqrAbsVectorX + $sqrAbsVectorY + \
 $sqrAbsVectorZ) ]

puts "To get from $hereNow to $thereThen you vector \
    ${X},${Y},${Z} for $distance"