Copy this code into a Ruby file, try running it, and then read the source code to see what it's doing.
def check_syntax(str)
openables = {
"(" => ")",
"[" => "]",
"{" => "}"
}
open = []
opening_chars = openables.keys
closing_chars = openables.values
str.each_char do |char|
if opening_chars.include?(char) # opening bracket
open << char
elsif closing_chars.include?(char) # closing bracket
required_char = openables[open.last]
if char == required_char # it's the right kind of closing bracket
open.pop
else
if open.any? # it's the wrong kind of closing bracket
puts "* You have a syntax error: there is an unexpected #{char}"
else # there's nothing to close
puts "* You have a syntax error: there is an unexpected #{char} where there is nothing to close."
end
return false
end
end
end
if open.any?
required_char = openables[open.last]
puts "* You have a syntax error: the string ended without a closing #{required_char}"
end
return open.empty?
end
puts check_syntax("(this)[] is some text")
puts "*****"
puts check_syntax("(this)] is some text")
puts "*****"
puts check_syntax("[(this] is some text")
puts "*****"
puts check_syntax("[this][ is some text")
puts "*****"
puts check_syntax("[this] is some text")
The output should currently look like this:
true
*****
* You have a syntax error: there is an unexpected ] where there is nothing to close.
false
*****
* You have a syntax error: there is an unexpected ]
false
*****
* You have a syntax error: the string ended without a closing ]
false
*****
true
Modify the code to improve the error messages it gives, specifying what character was missing. This should be your new output:
puts check_syntax("(this)[] is some text")
true
puts check_syntax("(this)] is some text")
* You have a syntax error: there is an unexpected ] where there is nothing to close.
false
New, improved error message:
puts check_syntax("[(this] is some text")
* You have a syntax error: there is an unexpected ] where there should be a )
false
puts check_syntax("[this][ is some text")
* You have a syntax error: the string ended without a closing ]
false
Modify the code to make it work for angled brackets (< and >) as well.
The new output for these strings containing angled brackets should look like this:
puts check_syntax("<html> (this)[] is some text</html>")
true
puts check_syntax("<html> (this)] is some text</html>")
* You have a syntax error: there is an unexpected ] where there is nothing to close.
false
puts check_syntax("<html> [(this] is some text</html>")
* You have a syntax error: there is an unexpected ] where there should be a )
false
puts check_syntax("<html> [this][ is some text</html")
* You have a syntax error: the string ended without a closing ]
false
puts check_syntax("<html> [this] is some text</html")
* You have a syntax error: the string ended without a closing >
false
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