Question

How Do I convert the below string/list to a list whose first element is 1-81 second element is 81-162 3rd element us 162-243 using tcl

{} {} {1 -81} { } {81 -162} { } {162 -243} { } {243 -324} { } {324 -405} { } {405 -486} { } {486 -567} { } {567 -648} { } {648 -729} { } {729 -810} { } {810 -891} { } {891 -972} { } {972 -1053} { } {1053 -1134} { }

Thanks

Answer 1

If you just want to filter out empty list elements, the obvious thing to do is:

# Assuming the original list is in $list

set result {}
foreach x $list {
    if {[string trim $x] != ""} {
        lappend result $x
    }
}

# The result list should contain the cleaned up list.

Note that you don’t need to do the [string trim] if you’re sure all empty elements really are empty and don’t contain whitespace (meaning {} instead of possibly { }). But your example contain both empty elements and whitespace so you need to do the string trim.

Alternatively you can use a regular expression to test:

foreach x $list {
    # Test if $x contains non-whitespace characters:
    if {[regexp {\S} $x]} {
        lappend result $x
    }
}

You can however do the above in a single line using lsearch:

# Find all elements that contain non whitespace characters:

set result [lsearch -inline -all -regexp $list {\S}]