I'm currently learning C programming, and wrote a script similar to one I've written in Python before. My goal is to learn how to pass input to an application and have it process the data I pass it.
The problem I'm having now is the feedback my application is giving me. I wrote a simple application to read keyboard input and give 1 of 3 responses based on what input I give it. The code is as follows:
/*Input test.*/
#include<stdio.h>
#include<stdlib.h>
char input;
const int option_a = 1;
const int option_b = 2;
int main()
{
printf("Lets get started! a for on or b for off?\n");
while(1)
{
input = getchar();
if(input == option_a)
{
printf("We're on.!\n");
}
else if(input == option_b)
{
printf("Off we go.\n");
}
else
{
printf("Excuse me, but I didn't get that.\n");
}
}
return 0;
}
Simply option_a is me pressing the 1 key on keyboard, and option_b is key 2. When I press these keys, or any key for that matter, the application will always go to the "else" portion of the decision tree. Saying that, it's clear to me that, and I'll say with a lack of a better term/expression, that my application isn't seeing my input as the decimal number 1 or 2.
From the terminal, what is the structure of the data I'm sending to my application, or simply put, what does my 1or 2 "look" like to my application?
When you are taking input with getchar() you are getting an char value. But you are comparing it with an integer. Instead of comparing with the integer, you can compare the input with corresponding characters. For example, use
const char option_a = '1';
const char option_b = '2';
I believe you want to find the American Standard Code for information interchange(ASCII) table. 0 = 48, 1 = 49, 2 = 50,...I had the same problem while working with arduino’s serial monitor, and it should all be covered by the same standard.
Related
I am trying to write a code that will loop you in case you provide wrong data. The problem is that I need to have some type of "Bad data" message for both 2 cases:
- you enter not an integer value
- you enter the value below 0
In this code if you type a letter, it loops you with a message: "Bad data", but if you type for example negative value like -10 Bad data is not appearing (even though validation works and you need to correct number to positive)
How can I do it more universal, so in both scenarios sysout with print on-screen Bad data
Random rand = new Random();
int los = rand.nextInt(11);
int NumberOfPlayers ;
Scanner scan7 = new Scanner(System.in);
System.out.println(" Type number of players :");
do {
while (!scan7.hasNextInt()){
System.out.println(" Bad data");
scan7.next();
}
NumberOfPlayers = scan7.nextInt();
}while (NumberOfPlayers < 0);
you are only validating if scanner has next int, you do not validate it's value, and integers can be negative.
try this solution:
do {
while (!scan7.hasNextInt()) {
System.out.println(" Bad data");
scan7.next();
}
NumberOfPlayers = scan7.nextInt();
if (NumberOfPlayers <= 0) {
System.out.println(" Number must be larger than zero");
}
} while (NumberOfPlayers <= 0);
After checking for next int, I added part checking value of provided int.
ALSO please remember about naming variables and classes - start with small letter, so in your case NumberOfPlayers should be numberOfPlayers.
Why you named scanner scan7? is there valid reason for that name? if no, you should avoid adding numbers to names.
I have some simple user input function which reads what the user types, ignoring any enter's and taking the first character it comes across. I am using the cin.ignore statement because this is part of a menu, and I want to replay the menu if they enter none of the given options, but only once. Now I basically want to have an if-statement which is true iff the user entered only one character (he may enter multiple enter's before this character), so I wanted to use something like sizeof or length, but I couldn't quite get it to work. Can anybody help with this? It would be much appreciated. Also, if anything should be changed about the phrasing of the question, please let me know. Thanks in advance.
char Interface::leesin ( ) {
char invoer;
do {
invoer = cin.get();
} while (invoer == '\n');
cin.ignore(MAX,'\n');
return invoer;
}
the following is a code snippet whereby the user will be presented with a console menu and needs to input a character. The cin will read in only 1 char and then the program can do some processing with this char. The loop will terminate, when the user inputs the char '9'.
#include <iostream>
using namespace std;
int main() {
char ch;
do {
//print menu here
cin >> ch; // take in one char only
//perform action based on ch
} while (ch != '9');
return 0;
}
I have a total of 6 booleans and the only thing separating them is a number. They're named checker0 though 5.
So checker0, checker1, checker2, checker3, checker4 and checker5.
All of these grants or denies access to certain parts of the app wether the bool is true or false.
I then have a randomiser using:
randomQuestionNumber = arc4random_uniform(5);
So say we get number 3, checker3 = true;
But my question now is would it be possible to set this one to true without having to go thru if statements.
My idea was to implement the way you print a int to say the NSLog using the %d.
NSLog(#"The number is: %d", randomQuestionNumber);
So something like:
checker%d, randomQuestionNumber = true.
Would something like that be possible? So i won't have to do like this:
if (randomQuestionNumber == 0) {
checker0 = true;
}
else if (randomQuestionNumber == 1)
{
checker1 = true;
}
Thanks you very much! :)
Every time you find yourself in a situation when you name three or more variables checkerN you know with a high degree of probability that you've missed a place in code where you should have declared an array. This becomes especially apparent when you need to choose one of N based on an integer index.
The best solution would be to change the declaration to checker[6], and using an index instead of changing the name. If this is not possible for some reason, you could still make an array of pointers, and use it to make modifications to your values, like this:
BOOL *ptrChecker[] = {&checker0, &checker1, &checker2, ...};
...
*ptrChecker[randomQuestionNumber] = true;
Currently the only way I know how to do input in D is with the scanf() function. But god damn it's ugly. You would think that since it's an upgrade from C that they would have fixed that.
I'm looking for a way to do it with a single argument. Currently you have to do:
int foo = 0;
scanf("%i", &foo);
writeln("%i", foo);
But it would look a lot cleaner with a single argument. Something like:
int foo = 0;
scanf(foo);
writeln(foo);
Thanks.
readf("%d", &foo); allows working with std.stdio.File rather than C FILE*
foo = readln().strip().to!int();
For reading entire files with lines formatted in the same way:
int[] numbers = slurp!int("filename", "%d");
There's a really cool user-input module here:
https://github.com/Abscissa/scriptlike/blob/master/src/scriptlike/interact.d
Example code:
if (userInput!bool("Do you want to continue?"))
{
auto outputFolder = pathLocation("Where you do want to place the output?");
auto color = menu!string("What color would you like to use?", ["Blue", "Green"]);
}
auto num = require!(int, "a > 0 && a <= 10")("Enter a number from 1 to 10");
The above answers are great. I just want to add my 2 cents.
I often have the following simple function lying around:
T read(T)()
{
T obj;
readf(" %s", &obj);
return obj;
}
It's generic and pretty handy - it swallows any white space and reads any type you ask. You can use it like this:
auto number = read!int;
auto floating_number = read!float;
// etc.
I have been developing a very simple text game using Objective C and Xcode. It is almost done but I am having a problem, the scanf method stops the loop and asks for user input while I need the computer to be running the rest of the loop, the solution I came up with was running two while loops at the same time, one being the logic loop and another being a loop for user input.
I have been doing my research and it looks like using threads are the way to go, I just have not found a tutorial that will break it down for a n00b in Objective C (I am decent in java, I just have never worked with threads). If anybody could explain them or link me to a very broken down tutorial that would be great. Or if anybody has another idea I am open to anything else.
Necessary Code (The scanf I am having a problem with has asterisks on the line):
while(running != 0)
{
if(gameState == 1)
{
if(timeToGenerateNum == true)
{
while(randNumber < 10000000)
{
randNumber = arc4random() % 100000000;
}
NSLog(#"%i", randNumber);
timeToGenerateNum = false;
}
else
{
while(time <= 2500)
{
NSLog(#"Testing");
time++;
******************scanf("%i", &userNum);************************
if(userNum == randNumber)
{
score += time;
time = 0;
timeToGenerateNum = true;
}
}
NSLog(#"Game Over! Your score was %i!", score);
running = 0;
}
}
else if(gameState == 2)
{
NSLog(#"To play, simply type in the number that appears on the screen.");
NSLog(#"But be careful, you only have a short amount of time before GAME OVER!");
NSLog(#"The quicker you type in the number the more score you get!");
NSLog(#"Are you ready to start, if so type '1' and press enter!");
scanf("%i", &gameState);
}
}
You're going to have to learn a bit about BSD (Unix, Linux) input/output to pull this off: replace your call to scanf with a non-blocking function you write to acquire input from the user's keyboard.
This function should immediately return whatever the user typed, or immediately return with a zero character count if she didn't type anything.
Read up on the select(2) system call, and keep in mind that keyboard input (standard input) is the first file descriptor, file descriptor zero.