Syntax error: invalid arithmetic operator (error token is ".txt") - bash

Question

I'm getting an error
Syntax error: invalid arithmetic operator (error token is ".txt")
at the if statement line. I check words_in_line by doing echo $words_in_line and it outputs numbers, so I don't understand why I'm getting this error. How do I fix this?
#!/usr/bin/env bash
#Outputs the lines that match wordcount range specified by min, $1, and max, $2
function get_correct_lines_in_file() {
while read line ; do
words_in_line=$( echo "$line" | wc -w );
if [[ words_in_line -ge $1 ]] && [[ words_in_line -le $2 ]]; then #ERROR HERE
echo "$line" >> MARBLES.txt
fi
done < $1
}
#Check if $1 and $2 arguments exists- are NOT NULL
if [[ "$1" != "" ]] && [[ "$2" != "" ]]; then
for i in ${*:3}
do
#If is a file you can read
if [[ -r $i && -f $i ]]; then
echo "$i exists and is readable"
get_correct_lines_in_file "$i"
#If file doesn't exist
elif [[ ! -f $i ]]; then
echo $i >> FAILED.log
fi
done
fi

Answer 1

If you want your minimum and maximum values to be accessible in your function, you need to pass them through. Consider accepting three arguments in your function, and explicitly passing the function's arguments through:
get_correct_lines_in_file() {
local -a words
while read -r -a words ; do
words_in_line=${#words[#]};
if (( words_in_line >= $2 )) && (( words_in_line <= $3 )); then
printf '%s\n' "${words[*]}"
fi
done <"$1" >>MARBLES.txt
}
...and later, passing the filename to be the function's $1, the script's $1 to be the function's $2, and the script's $2 to be the function's $3:
get_correct_lines_in_file "$i" "$1" "$2"