wdb -- looking for list comparison similar to equal? in Scheme, I found that it is surprisingly difficult due to the lack of types. Here my approach in Tcl. The procedure lequal checks recursively on elementwise equality:
proc lequal {a b} {
if {![string is list $a]} then {
string equal $a $b
} elseif {![string is list $b]} then {
return 0
} elseif {[llength $a] != [llength $b]} then {
return 0
} elseif {[llength $a] == 0} then {
return 1
} elseif {[llength $a] > 1} then {
expr {[lequal [lindex $a 0] [lindex $b 0]]] &&
[lequal [lrange $a 1 end] [lrange $b 1 end]]]}
} elseif {$a eq [lindex $a 0] || $b eq [lindex $b 0]} then {
string equal $a $b
} else {
lequal [lindex $a 0] [lindex $b 0]
}
}
Don't know if in real life necessary, but by reasons of completeness, I did it.