Arjen Markus (16 april 2018) Lucky numbers are akin to prime numbers in that they are constructed via a sieve process too. They even have statistically similar properties. See
this page on Mathworld
for instance. The process is simple enough:
- Start with the odd numbers:
1, 3, 5, 7, 9, 11, 13, 15, 17, 19, ...
- Then, the second number in that list is 3, so remove every third number:
1, 3, 7, 9, 13, 15, 19, ...
- Then, the third number is 7, so remove every seventh number:
1, 3, 7, 9, 13, 15, ...
Thanks to the [lmap] command, the implementation in Tcl is also simple:
set numbers {}
for {set i 1} {$i < 1000} {incr i 2} {
lappend numbers $i
}
#
# Loop over the remaining elements in the list:
# Filter out the nth element each time - a simple job for [lmap]
#
for {set k 1} {$k < [llength $numbers]} {incr k} {
set step [lindex $numbers $k]
set i 0
set numbers [lmap v $numbers {
incr i
if {$i % $step} {
set v
} else {
continue
}
}]
}
puts $numbers
