ruby - Beginner array iteration & error code interpretation -

-

i kept getting following error. after research assumed because array access throwing error due (mistakenly) having nil value.

my_solution.rb:24:in `count_between': undefined method `>=' nil:nilclass        (nomethoderror) my_solution.rb:35:in `<main>'

i'm new reading error codes, perhaps that's went wrong. got tunnel vision on line 24, error suggested. couldn't fix it, out of desperation wound randomly changing (<=) on line 23 (<). fixed it.

  1. why did fix it? guess using (<=) made iterate "too far" , somehow returned nil?

  2. why did error code element on line 24 causing issue, when element on line 23? i'm new , trying less intimated error codes, curious experience.

thanks guidance.

# count_between method 3 arguments: #   1. array of integers #   2. integer lower bound #   3. integer upper bound # # returns number of integers in array between lower , upper           # bounds, # including (potentially) bounds. # # if +array+ empty method should return 0 # solution below:  def count_between(list_of_integers, lower_bound, upper_bound) if list_of_integers.empty?    return 0 else    count = 0    index = 0     ##line 23##     while index <= list_of_integers.length     ##line24##         if list_of_integers[index] >= lower_bound &&            list_of_integers[index] <= upper_bound              count += 1             index += 1        else             index += 1        end     end   return count end end  puts count_between([1,2,3], 0, 100)

the last index that's <= list_of_integers.length outside of array, since first index of array 0 , last array.length - 1.

the reason error says line 24 line 23 works fine --- computes value of index less or equal the length of array. once try , reference element @ index in array, however, it's assigned nil - , can't perform >= operation on nil.

one thing might helpful here firing irb. if try reference element that's out of bounds, you'll nil. if try , perform operation (that's not listed in nil.methods) on same reference, it'll throw error you're seeing.


Comments

Post a Comment

Popular posts from this blog

c++ - No viable overloaded operator for references a map -

-
i trying use map can make tag names reference number. when try , use it, in code error (6 in total every time reference map): src/main.cpp:25:45: error: no viable overloaded operator[] type 'std::map<std::string, std::string>' const char* idcs = node.child_value(tagmap[3]); this code: #include "pugi/pugixml.hpp" #include <iostream> #include <string> #include <map> int main() { pugi::xml_document doca, docb; std::map<std::string, pugi::xml_node> mapa, mapb; std::map<std::string, std::string> tagmap {{"1", "data"}, {"2", "entry"}, {"3", "id"}, {"4", "content"}}; if (!doca.load_file("a.xml") || !docb.load_file("b.xml")) { std::cout << "can't find input files"; return 1; } (auto& node: doca.child(tagmap[1]).children(tagmap[2])) { co
Read more

java - Custom OutputStreamAppender not run: LOGBACK: No context given for <MYAPPENDER> -

-
i wish write custom appender on basis of outputstreamappender . wrote following class package tests; import java.io.ioexception; import java.io.outputstream; import ch.qos.logback.core.outputstreamappender; public class myappender<e> extends outputstreamappender<e> { public myappender() { system.out.println("myappender created"); setoutputstream(new outputstream() { @override public void write(int b) throws ioexception { throw new unsupportedoperationexception(); } }); } } then wrote following runner: package tests; import org.slf4j.loggerfactory; import ch.qos.logback.classic.logger; public class runner { private static final logger log = (logger) loggerfactory.getlogger(runner.class); public static void main(string[] args) { //log.addappender(new myappender<iloggingevent>()); log.info("hello world"); } } finall
Read more

java - Cannot secure connection using TLS -

-
i'm trying establish secure socket connection between java client applet (built jdk 1.7.0_75-b13) , vc++ server application. as test vehicle, used vc++ client/server sample found in msdn forums, modified use schannel , able establish socket using cipher suite tls_rsa_with_aes_128_cbc_sha. works of tls 1.0/1.1/1.2. when try opening socket java applet same server application, connection rejected server reporting following: tls 1.0 acceptsecuritycontext failed: 0x80090327 tls 1.1 acceptsecuritycontext failed: 0x80090331 tls 1.2 acceptsecuritycontext failed: 0x80090331 this java code used create socket: debugprint("setting secure connection"); sslsocketfactory sslsocketfactory = (sslsocketfactory) sslsocketfactory.getdefault(); sslsocket sslsocket = (sslsocket) sslsocketfactory.createsocket("127.0.0.1", socketnumber); debugprint("starting handshake"); sslsocket.settcpnodelay(true); sslsocket.setsolinger(false, 0); sslsocket.s
Read more