While loop not exiting when condition is true / missing part of the output

[Maroine81]

Oh man! while loops! they give me chills when I think about 'em ^^ I'm hoping someone will provide his/her insight into why the following error/behavior.

I tested this while loop in the debugger and got an error when i = 2 and j = 11 at the end while line, stating that members[11] is not found which is true. The problem is that the while loop doesn't exit when j = 11. When I remove the equal sign in the while loop like this

while (j < 10 .and. (members[j].ID == groups[i].ID) )

the error is not produced because it doesn't test members[11] and the output misses to add an extra data that is supposed to be there.

for i = 1 to 3
    
    for j = 1 to 10
        
        while (j <= 10 .and. (members[j].ID == groups[i].ID) )
          *array_append(groups[i].PEOPLE,members[j])
          j = j + 1

      [COLOR=#ff0000]  end while     ' Error Occurred        Not found members [] not found [/COLOR]

         if (variable_exists("groups[i].PEOPLE") <> .t.) then
              'some code
          end if
          
    next j
     
next i

I also tried it like this and I didn't get an error but the output skips to check for i=2 and j=6,7,8,9,10 which results into a incomplete output. for instance when i=2 and j=6 the while condition is true but it is not checked, it's just skipped it only checks for i but not for j. I must be missing something.

dim j as n = 1
    for i = 1 to 3
        while (j <= 10 .and. members[j].ID == groups[i].ID) 
            *array_append(groups[i].PEOPLE,members[j])
             j = j + 1
        end while
 
    if (variable_exists("groups[i].PEOPLE") <> .t.) then
      'some code
    end if
 
    next i

Thanks for taking the time for looping around this post ^^

[Stan Mathews]

Re: While loop not exiting when condition is true / missing part of the output

Bit of a kludge but how about

for i = 1 to 3
    
    for j = 1 to 10
        
        while (j <= 10 .and. (members[j].ID == groups[i].ID) )
        if j < 11
          *array_append(groups[i].PEOPLE,members[j])
          j = j + 1
        end if
        end while     ' Error Occurred        Not found members [] not found 

         if (variable_exists("groups[i].PEOPLE") <> .t.) then
              'some code
          end if
          
    next j
     
next i

[Maroine81]

Re: While loop not exiting when condition is true / missing part of the output

Thanks Stan

I've just tested it & it's still producing the same error.
i=2, j=10 and members[10].ID = groups[2].ID, the array_append happens then j becomes 11 end if end while Error occurs Not Found Members[] not found.

Is there away to achieve what I'd like to achieve without either using the while loop or without putting members[j].ID == groups[i].ID inside the while loop 'cause that's what's causing the error. j becomes 11 and at the end of the while loop it checks whether the statement members[11].ID == groups[2].ID is true or not then it produces the error since members[11] doesn't exist. there are only 10 members.

[Maroine81]

Re: While loop not exiting when condition is true / missing part of the output

I've just found a workaround ^^ I removed the condition that caused the error in the while loop and added it in an if statement after the while loop to append the array in case it is true

for i = 1 to 3
    
    for j = 1 to 10
        
        while (j < 10 .and. (members[j].ID == groups[i].ID) )
        
          *array_append(groups[i].PEOPLE,members[j])
          j = j + 1

        end while
        
        if (j=10 .and. (members[j].ID == groups[i].ID))
            *array_append(groups[i].PEOPLE,members[j])
        end if

         if (variable_exists("groups[i].PEOPLE") <> .t.) then
              'some code
          end if
          
    next j
     
next i

[RichCPT]

Re: While loop not exiting when condition is true / missing part of the output

I don't know what you are trying to accomplish, but I would not increment the "j" variable explicitly inside a "for" loop - that is what the "next j" line does.

In your example you either you don't need the "while" loop or you need to add an extra variable.

[Stan Mathews]

Re: While loop not exiting when condition is true / missing part of the output

the array_append happens then j becomes 11

I must be missing something. I don't see how the array_append can happen when j becomes 11 because there is an explicit test to not to do anything unless j < 11

if j < 11
          *array_append(groups[i].PEOPLE,members[j])
          j = j + 1
        end if

Glad you found your workaround.

[RichCPT]

Re: While loop not exiting when condition is true / missing part of the output

Also, has "groups[i].PEOPLE" been dimmed some where to be an array?

[Maroine81]

Re: While loop not exiting when condition is true / missing part of the output

I must be missing something. I don't see how the array_append can happen when j becomes 11 because there is an explicit test to not to do anything unless j < 11

for i = 1 to 3
    
    for j = 1 to 10
        
        while (j <= 10 .and. (members[j].ID == groups[i].ID) )
        if j < 11
          *array_append(groups[i].PEOPLE,members[j])
          j = j + 1
        end if
        end while     ' Error Occurred        Not found members [] not found 

         if (variable_exists("groups[i].PEOPLE") <> .t.) then
              'some code
          end if
          
    next j
     
next i

Glad you found your workaround.

Stan, you didn't miss anything. The array_append didn't happen when j=11. Let me clarify how the error occurs. When j =10 and (members[10].ID == groups[i].ID) for some value of i, the if statement is also true 10<11 the array append happens then j becomes 11. When the code reaches END WHILE that's when the error occurs because it checks then that members[11] doesn't exist. I don't know why it checks at the end of while but it does.

I'm glad I've found a workaround too ^^ Thanks again for your suggestion though I appreciate it.

[Maroine81]

Re: While loop not exiting when condition is true / missing part of the output

I don't know what you are trying to accomplish, but I would not increment the "j" variable explicitly inside a "for" loop - that is what the "next j" line does.

In your example you either you don't need the "while" loop or you need to add an extra variable.

Rich, you're right normally, incrementing explicitly the "j" variable inside a "for" loop is not recommended, but in this case, I needed to add specific members to PEOPLE in different groups. I got it working and I've tested it with different input variables & it's outputting the desired result It's supposed to output.

Also, has "groups[i].PEOPLE" been dimmed some where to be an array?

Yes, It was dimmed as dim groups[0] as p otherwise it'd have given me a groups[] not found. The error was that members[] is not found at the end of the while loop when j=11, which is true since there is no member[11] only 10 members.

Thanks for taking the time to reply though, I do appreciate it.

[GGandhi]

Re: While loop not exiting when condition is true / missing part of the output

it is not clear why you need a while loop inside a for loop to do the same thing ( for loop runs 10 times and while loop runs the same )
can you not rewrite the code

dim i as n
dim j as n
for i = 1 to 3
	for j = 1 to 10
		 if (members[j].ID == groups[i].ID) 
                     *array_append(groups[i].PEOPLE,members[j])
         	      if (variable_exists("groups[i].PEOPLE") <> .t.) then
                      'some code
                   end if
              end if
	next j
next i

and get the same results?

still i am happy you found a solution to problem, just was curious.

[Stan Mathews]

Re: While loop not exiting when condition is true / missing part of the output

I think I see it now. The while loop is always checking the value of j to decide whether to end or not. When j becomes 11 due to

j = j + 1

then the while looks at while (j <= 10 .and. (members[j].ID == groups[i].ID) ) and has to evaluate both tests

and since there is no members[11].ID

you get the error.

[Maroine81]

Re: While loop not exiting when condition is true / missing part of the output

it is not clear why you need a while loop inside a for loop to do the same thing ( for loop runs 10 times and while loop runs the same )
can you not rewrite the code

dim i as n
dim j as n
for i = 1 to 3
	for j = 1 to 10
		 if (members[j].ID == groups[i].ID) 
                     *array_append(groups[i].PEOPLE,members[j])
         	      if (variable_exists("groups[i].PEOPLE") <> .t.) then
                      'some code
                   end if
              end if
	next j
next i

and get the same results?

still i am happy you found a solution to problem, just was curious.

Govindan Gandhi, your code works perfectly! Simple, clean & fewer iterations. It outputs the desired result.

I've just substituted the one I had using the while loop with yours.

Thank you