Re: good to know: tcl static "regexp" is faster than tcl "string" operation

aotto1968 <aotto1968@t-online.de> wrote:

#!/usr/bin/env tclsh
>
proc test-1 { val } {
   if {[regexp ^:: $val]} {
     return true
   } else {
     return false
   }
}
>
proc test-2 { val } {
   if {[string range $val 0 1] eq "::"} {
     return true
   } else {
     return false
   }
}
>
set num 100000
puts 1=[time {test-1 ::otto} $num]
puts 2=[time {test-1 otto}   $num]
puts 3=[time {test-2 ::otto} $num]
puts 4=[time {test-2 otto}   $num]
>
>

./sbin/time-check.tcl

1=1.26311 microseconds per iteration
2=1.09152 microseconds per iteration
3=1.44028 microseconds per iteration
4=1.43917 microseconds per iteration

 But neither is quite as fast as string match (athough regex is close):
 $ cat time-check.tcl
#!/usr/bin/env tclsh
 proc test-1 { val } {
   if {[regexp ^:: $val]} {
     return true
   } else {
     return false
   }
}
 proc test-2 { val } {
   if {[string range $val 0 1] eq "::"} {
     return true
   } else {
     return false
   }
}
 proc test-3 { val } {
   return [string match ::* $val]
}
 set num 100000
puts 1=[time {test-1 ::otto} $num]
puts 2=[time {test-1 otto}   $num]
puts 3=[time {test-2 ::otto} $num]
puts 4=[time {test-2 otto}   $num]
puts 5=[time {test-3 ::otto} $num]
puts 6=[time {test-3 otto}   $num]
 $ ./time-check.tcl
1=0.45252 microseconds per iteration
2=0.42354 microseconds per iteration
3=0.58949 microseconds per iteration
4=0.58363 microseconds per iteration
5=0.4351 microseconds per iteration
6=0.41378 microseconds per iteration