multidimensional array search in tcl - tcl

Question

I am using multidimensional associative array in tcl ,from fourth column to N column I am storing values and i will compare each of those with second column and store the result in third column for each of row's values.Sometimes it searches the perfectly sometimes it skips the values and gives out error.Is there any better way to search in multidimensional array in tcl ? What is the problem with this code?
for {set index 1} {$index < $count} {incr index} {
for {set val 3} {$val < $d1 } {incr val} {
if {$flag1 != 1} {
if {$asarr($index,2)== $asarr($index,$val)} {
set asarr($index,1) 50
} else {
set asarr($index,1) 100
set flag1 1
break
}
}
}
set flag1 0
}

Answer 1

There is a discrepancy between your code and the problem explanation in your question.
From your question I summarise these requirements:
data is stored in 2 dimensional array
each row stores one set of data
within each row, data is stored in columns where:
1st column is not mention in the original question
2nd column contains a value against which all 'data columns' will be compared
3rd column is where the result of the comparison will be stored (looking at the code, result is either a 50 or a 100)
4th to Nth column hold the data that needs to be compared against value of 2nd column
And this is what your code actually does:
# start iterating array by rows
# first row has index 1
for {set index 1} {$index < $count} {incr index} {
# start iterating over columns
# NOTE: either column indexes are assumed to start at 0
# or we, in fact, start with the 3rd column instead of 4th
for {set val 3} {$val < $d1 } {incr val} {
# check the special flag named 'flag1'
# NOTE: it would be better to give it a meaningful name
# such as 'found' since it signals that we found
# an element equal to the one in 2nd column
if {$flag1 != 1} {
if {$asarr($index,2)== $asarr($index,$val)} {
# if the element at current position ($index,$val)
# is equal to the element at ($index,2)
# write '50' at ($index,1)
# NOTE: result is stored in 1st column,
# not in 3rd as the question would assume
set asarr($index,1) 50
} else {
# if the current element is not equal to the one
# in 2nd column, write '100' at ($index, 1).
# Again, this is not the 3rd column as requested originally
set asarr($index,1) 100
# set the special flag to 1, meaning that the above
# IF clause will not be run again
set flag1 1
# execute a break, meaning that we immediately interrupt
# the inner FOR loop, meaning that the above IF clause
# will not be run again in this iteration.
# As Donal pointed out, you could completely
# remove the $flag1 and achieve the same result with
# this break clause
break
}
}
}
# reset the flag so that IF clause is executed at least once
# for the next iteration of the outer loop
set flag1 0
}
If we assume that the 'flag1' is set to 0 (or anything != 1) before the FOR loops start, then the end result is that the code iterates through array rows, compares each column (starting from 3rd!) against column number 2, it repeats this for all other columns BUT ONLY if their values are equal to column 2 and EACH TIME OVERWRITES THE SAME value '50' over column 1. As soon as a different value is encountered, the result '100' is written to column 1 and the rest of the values are immediately skipped. Execution then starts from the beginning but with the next row.
How does that compare against your original intentions?
The code could (and should) be greatly simplified at least so it doesn't overwrite the same value many times, however, I am not exactly sure what you are trying to achieve. Please try to clarify your requirements.
I don't know if this will be useful (you said that the code does not behave as you would like it to), but here is an alternative version that behaves according to the requirements I guessed from your question (and listed above):
for {set index 1} {$index < $count} {incr index} {
set asarr($index,3) 50
for {set val 4} {$val < $d1 } {incr val} {
if {$asarr($index,2)!= $asarr($index,$val)} {
set asarr($index,3) 100
break
}
}
}