[CentralOH] One Change Too Far: Got Rid of Temporary Variable

[jep200404 at columbus.rr.com]

On Sat, 21 Oct 2017 01:11:18 -0400, jep200404 at columbus.rr.com wrote:

>           set c [expr $a + $b]
>           set a $b
>           set b $c

Below: One change too far:

    Get rid of the temporary variable c that is above.

It is interesting that it can be done at all.
But golly, it sure is hard to understand how the program works now.
The extra calculation also makes the program slower
than the one that used the temporary variable.

Also uses shebang.

    doj at sbc:~/20171020$ cat fib-without-c.tcl
    #!/usr/bin/env tclsh

    proc fib {n} {
       set a 0
       set b 1
       for {set i 0} {$i < $n} {incr i} {
          set b [expr {$a + $b}]
          set a [expr {$b - $a}]
       }
       return $a
    }

    puts "Please enter seed value:"

    gets stdin x

    set StartTime [clock microseconds]
    set Answer [fib $x]
    set EndTime [clock microseconds]
    puts "Seed $x; Result $Answer"
    puts "Duration [expr $EndTime - $StartTime] microseconds"
    doj at sbc:~/20171020$ 

    doj at sbc:~/20171020$ diff fib-with-braces.tcl fib-without-c.tcl
    7,9c7,8
    <       set c [expr {$a + $b}]
    <       set a $b
    <       set b $c
    ---
    >       set b [expr {$a + $b}]
    >       set a [expr {$b - $a}]
    doj at sbc:~/20171020$ 

    doj at sbc:~/20171020$ echo 11111 | time ./fib-without-c.tcl
    Please enter seed value:
    Seed 11111; Result 515...489
    Duration 81068 microseconds
    0.11user 0.00system 0:00.11elapsed 97%CPU (0avgtext+0avgdata 4940maxresident)k
    0inputs+0outputs (0major+356minor)pagefaults 0swaps
    doj at sbc:~/20171020$