sync lists

#!/usr/bin/env tclsh

set input1 {SYNC 1 1;SYNC 2 2;K1_SP4_SPA_FINISH_TURN 4}
set input2 {SYNC 1 1;K2_SP4_SPA_GROOVE_OD 4;K2_SP4_SPA_SQUARE_SIDE_3_CUTCOM_SPA_DRILLING_FRONT 4;SYNC 2 2}

set L1 [split $input1 ";"]
set L2 [split $input2 ";"]

set out1 [list]
set out2 [list]

set i1 0
set i2 0
while {$i1 < [llength $L1] || $i2 < [llength $L2]} {
    set tmp1 [lindex $L1 $i1]
    set tmp2 [lindex $L2 $i2]

    if {[string match SYNC* $tmp1] && [string match SYNC* $tmp2]} {
	lappend out1 $tmp1
	lappend out2 $tmp2
	incr i1
	incr i2
	continue
    }

    if {[string match SYNC* $tmp1]} {
	# Out of sync -- list 1 is "ahead".  Add a NOOP to output list 1.
	# Only advance in list 2.
	lappend out1 NOOP
	lappend out2 $tmp2
	incr i2
	continue
    }

    if {[string match SYNC* $tmp2]} {
	# Opposite of above.
	lappend out1 $tmp1
	incr i1
	lappend out2 NOOP
	continue
    }

    # Otherwise, we just advance normally in each list.
    lappend out1 $tmp1
    lappend out2 $tmp2
    incr i1
    incr i2
}

puts "out1: $out1"
puts "out2: $out2"