Visit Our UNIX and Linux User Community


Code review: recursion in circular array, reduce two functions to one?


 
Thread Tools Search this Thread
Top Forums Programming Code review: recursion in circular array, reduce two functions to one?
# 1  
Old 03-22-2018
Code review: recursion in circular array, reduce two functions to one?

Hello,
I think there's an easier way to do this but can't seem to recall but given an array of animals[0...5] and an initial value is a random index in the array, here it's 3.

3,4,5,4,3,2,1,0,1,2,3,4,5,4,3,2,1,0... inifinite repeat

a quick brute force solution i came up with was two functions, i set a limit of 20 so it doesn't become a memory bomb. there would be some kind of other conditional break point.

Code:
func fwd()
{
  counter += 1
  while(currentRow < (animals.count - 1))
  { currentRow += 1 }
  if counter < 20 { bk() }
}

func bk()
{
  counter += 1
  while(currentRow > 0)
  { currentRow -= 1 }
  if counter < 20 { fwd () }
}

fwd()


Last edited by f77hack; 03-22-2018 at 09:44 PM.. Reason: typos
# 2  
Old 03-23-2018
That spec is beyond me. Mayhap others, with some assumptions on e.g. shell and data structure, find a sensible interpratation of what you write.

For an index not to exceed array boundaries the modulo operator has proven quite helpful.
This User Gave Thanks to RudiC For This Post:
# 3  
Old 03-23-2018
Maybe you could have an adjustment value that you would always add. When the counter gets high, you set the adjustment value to -1. When it gets back to zero, you set it to 1. That way, you only have one function plus a decision to make about if you need to change the adjustment value:-
Code:
adjval=1
counter=0
currentRow=0

function adjust_it ()
{
 ((counter=$counter+1))
 ((currentRow=$currentRow+$adjval))
 [ $currentRow -le 0 ] && adjval=1                # We set it to count up
 [ $currentRow -ge 5 ] && adjval=-1               # We set it to count down
 echo "Counter is $counter ; CurrentRow is $currentRow ; Adjustment value is $adjval"
}

Then, a simple loop will illustrate it:-
Code:
$ while :
> do
> adjust_it
> sleep 1
> done
Counter is 1 ; CurrentRow is 1 ; Adjustment value is 1
Counter is 2 ; CurrentRow is 2 ; Adjustment value is 1
Counter is 3 ; CurrentRow is 3 ; Adjustment value is 1
Counter is 4 ; CurrentRow is 4 ; Adjustment value is 1
Counter is 5 ; CurrentRow is 5 ; Adjustment value is -1
Counter is 6 ; CurrentRow is 4 ; Adjustment value is -1
Counter is 7 ; CurrentRow is 3 ; Adjustment value is -1
Counter is 8 ; CurrentRow is 2 ; Adjustment value is -1
Counter is 9 ; CurrentRow is 1 ; Adjustment value is -1
Counter is 10 ; CurrentRow is 0 ; Adjustment value is 1
Counter is 11 ; CurrentRow is 1 ; Adjustment value is 1
Counter is 12 ; CurrentRow is 2 ; Adjustment value is 1
Counter is 13 ; CurrentRow is 3 ; Adjustment value is 1
Counter is 14 ; CurrentRow is 4 ; Adjustment value is 1
Counter is 15 ; CurrentRow is 5 ; Adjustment value is -1
Counter is 16 ; CurrentRow is 4 ; Adjustment value is -1
Counter is 17 ; CurrentRow is 3 ; Adjustment value is -1
Counter is 18 ; CurrentRow is 2 ; Adjustment value is -1
Counter is 19 ; CurrentRow is 1 ; Adjustment value is -1
Counter is 20 ; CurrentRow is 0 ; Adjustment value is 1
Counter is 21 ; CurrentRow is 1 ; Adjustment value is 1
Counter is 22 ; CurrentRow is 2 ; Adjustment value is 1
Counter is 23 ; CurrentRow is 3 ; Adjustment value is 1
Counter is 24 ; CurrentRow is 4 ; Adjustment value is 1
Counter is 25 ; CurrentRow is 5 ; Adjustment value is -1
Counter is 26 ; CurrentRow is 4 ; Adjustment value is -1
Counter is 27 ; CurrentRow is 3 ; Adjustment value is -1
Counter is 28 ; CurrentRow is 2 ; Adjustment value is -1
Counter is 29 ; CurrentRow is 1 ; Adjustment value is -1



Does that help, or have I missed the point?
Robin
This User Gave Thanks to rbatte1 For This Post:
# 4  
Old 03-23-2018
Code:
#!/bin/bash

max=5

next() {
  [ $counter -eq 0    ] || [ -z "$last" ] && change="1"
  [ $counter -eq $max ]                   && change="-1"
  last=$counter
  ((counter=$counter + $change))
}

counter=$(($RANDOM%($max+1)))
for((i=0;$i<20;i++));do
        echo $counter
        next
done

Remark
Don't use global variables like this in a bigger script!

Last edited by stomp; 03-23-2018 at 08:55 AM..
This User Gave Thanks to stomp For This Post:
# 5  
Old 03-23-2018
The recursion seems strange.
Better go for an iteration: an outer loop with counter, and two loops inside (one fwd then one bk).
BTW this is not shell code...
This User Gave Thanks to MadeInGermany For This Post:
# 6  
Old 03-23-2018
Quote:
Originally Posted by rbatte1

Does that help, or have I missed the point?
Robin
Hello Robin, that definitely helps. The original code is swift but I don't mind if code is bash, perl... I just need to see some code that works.
Thank you.

---------- Post updated at 03:34 PM ---------- Previous update was at 03:25 PM ----------

Quote:
Originally Posted by RudiC
For an index not to exceed array boundaries the modulo operator has proven quite helpful.
Thanks for the input. I gave that a try but couldn't quite work out how to flip the counter to count down negative. I'm not that informed on how to flip the pointer.

---------- Post updated at 03:38 PM ---------- Previous update was at 03:34 PM ----------

Quote:
Originally Posted by stomp
Remark
Don't use global variables like this in a bigger script!
Thank you.

Last edited by f77hack; 03-23-2018 at 05:34 PM.. Reason: typo
# 7  
Old 03-24-2018
Ohhh - got it . . . Try - recent bash (ksh) required -
Code:
animals=(Lion Tiger Panther Cougar Cheetah Leopard)
DLT=1
IDX=3
for i in {1..20}
  do    echo $IDX: ${animals[IDX]}
        (( IDX % (${#animals[@]}-1) )) || (( DLT *= -1 ))
        (( IDX += DLT))
  done
3: Cougar
4: Cheetah
5: Leopard
4: Cheetah
3: Cougar
2: Panther
1: Tiger
0: Lion
1: Tiger
2: Panther
3: Cougar
4: Cheetah
5: Leopard
4: Cheetah
3: Cougar
2: Panther
1: Tiger
0: Lion
1: Tiger
2: Panther


Last edited by RudiC; 03-24-2018 at 10:10 AM..
This User Gave Thanks to RudiC For This Post:

Previous Thread | Next Thread
Test Your Knowledge in Computers #713
Difficulty: Medium
The shared bus between the program memory and data memory leads to the von Neumann bottleneck, the limited throughput (data transfer rate) between the CPU and memory compared to the amount of memory.
True or False?

9 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Reduce the number of lines by using Array

I have the following code to count the number of how many times the name occurred in one file. The code is working fine and the output is exactly what I want. The problem is the real code has more than 50 names in function listname which cause function name to have more than 50 case ,and function... (14 Replies)
Discussion started by: samsan
14 Replies

2. Shell Programming and Scripting

Need help on Assigning a Array variable from Background Functions

I have a question on how can I assign a output of a function to a variable which is executed in background. Here is my example $ cat sample_program.sh #!/bin/ksh exec_func () { sleep 1 v=`expr $1 + 100` print $v } export OUT_ARR date for i in 1 2 do OUT_ARR=`exec_func $i` &... (1 Reply)
Discussion started by: mohan_kumarcs
1 Replies

3. Programming

c++ code to check whether a list is circular or not

hi all, i need c++ code to check whether a list is circular or not... please help (8 Replies)
Discussion started by: vidyaj
8 Replies

4. Shell Programming and Scripting

Passing array to functions in ksh script

Let me know if there is a way to pass array to a funtion in ksh script. function isPresent { typeset member member=$1 dbList=$2 echo '$1:' $1 echo '$2' $dbList The array will be at the second position....something like this isPresent 12 <array> if then echo... (3 Replies)
Discussion started by: prasperl
3 Replies

5. Shell Programming and Scripting

How to reduce code.....

Hi All, Could some one help me to reduce the code... if then ./plist -m "$queuename" |grep $2|awk '{print $3}' >unlock.log elif then ./plist -m "$queuename" |grep $2|awk '{print $4}' >unlock.log else ./plist -m "$queuename" |grep $2|awk '{print $5}' >unlock.log . . . . ... (1 Reply)
Discussion started by: harshakusam
1 Replies

6. Programming

[ C ] multidemensional array pass to functions

Please excuse my ineptitude for a bit as I've been spoiled for the past few months with only writing perl code instead of C. So ok, I've been thinking about some code to change the crc32 values that are held within central directory headers of zip files. Because I'm lazy I decided to just... (3 Replies)
Discussion started by: VRoemer
3 Replies

7. Shell Programming and Scripting

Tricky array substitution in functions

Hello, Please tell me if there is a better way to get the number of elements from an array that is passed to a function. This is what works on Solaris 8 (ksh) but it looks odd: loop_array() { array_name=$2 b1='\${\#' b2='}' nr_elements=`eval echo... (6 Replies)
Discussion started by: majormark
6 Replies

8. Shell Programming and Scripting

Can someone review my code tell me where I am going wrong?

Started writing my code. my read input is not even asking nor working? And I get a EOF script error. echo "1) aragorn.domain.net" echo "2) marvel.domain.net" echo "3) athena.domain.net" echo "4) gandalf.domain.net" echo "5) griffin.domain.net" echo "What server would you like... (4 Replies)
Discussion started by: chrchcol
4 Replies

9. Shell Programming and Scripting

Can some review my code would be appreicated?

I am getting an error "ftpNotes.sh: syntax error at line 8 : `<<' unmatched" #!/bin/ksh PATH=/usr/sbin/:/usr/bin:/usr/ucb:/etc:/usr/local/bin:. cd $HOME if ;then if ; then echo 'DSC file already ftp to epm server' else ftp -n epmdev00 <<SCRIPT... (1 Reply)
Discussion started by: sibghat
1 Replies

Featured Tech Videos