jQuizMe Example: Simple Math Quiz


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Here’s an example of jQuizMe.
Goal: Make a quiz for Addition, Subtraction and Multiplication for two digit numbers.

Steps:

  1. Make a random number generator.
  2. Make a function to form a question and answers.
  3. Form the quiz.
  4. Call jQuizMe

Step 1:
I wrote a random number generator in javascript here.

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var getRandomNum = function( i, decLen ){
	var powOf10s = Math.pow( 10, decLen || 0 );
	return i ?  Math.floor( powOf10s * Math.random() * i ) / powOf10s : Math.random();
};

Or.. you could just use Math.floor( Math.random() * number ).

Step 2 & 3: (Due to time constraints I combined step 2 and 3.)

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var link = "http://bateru.com/news/2011/04/learn-sig-figs-in-no-time/";
var ops = operations = [ " + ", " - ", " * ", " / " ];
var precision = 2;
 
var arrOfRandomNum = function( arrLength, max, decLen ){
	if( arrLength < 0 ){ return false; }
	var arr = [], i = arrLength;
	while( i-- ){
		arr[ i ] = getRandomNum( max, decLen );
	}
	return arr;
};
var makeQuiz = function(){
	var quiz = { "fill":[] };
	var question = '', nums = [];
	var i = questionLength = 10;
	while( i-- ){
		nums = arrOfRandomNum( 2, 19 );
		question = nums.join( ops[ getRandomNum( ops.length ) ] );
		quiz.fill.push({
			ques: question,
			ans: eval( question ).toPrecision(precision)
		});
	}
	return quiz;
}

Step 4:

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$( "#quiz" ).jQuizMe( makeQuiz(), {
	intro: ops.join(',') + " quiz.<br>Note: Your answer must have " + precision + " <a href='"+link+"'>sig figs</a>."
});

Here’s the working demo.

Code of the day: C, Get the Digits from a Number

Today’s Code of the Day is about how to find the digit of a number at a given position. I decided to go with the C / C++ programming languages to time, but you can easily translate the algorithms to other languages.

C Code.

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#include <stdio.h>
#include <math.h>
 
// Function: getDigitFromNum returns a digit at a given index of a integer.
// Goes from right to left with the starting index of 0.
int getDigitFromNum( int num, int digit ){
    num /= pow( 10, digit );
    return num % 10;
}
// Function: getDigitFromDec returns a digit at a given index of a double.
// Goes from left to right with the starting index of 0.
int getDigitFromDec( double dec, int digit ){
    dec *= pow( 10, digit );
    return (int)dec % 10;
}
// Function: getDigitFromNum returns the decimal values of a double.
double getDecimals( double dec ){
    return dec - (int)dec;
}

Example:
Input File

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// Programmed by Larry Battle, bateru.com/news
// Date: April 26, 2011
// Purpose: To demonstrate how to get a digit by a position index.
#include <stdio.h>
#include <math.h>
 
int getDigitFromNum( int num, int digit ){
    num /= pow( 10, digit );
    return num % 10;
}
int getDigitFromDec( double dec, int digit ){
    dec *= pow( 10, digit );
    return ((int)dec) % 10;
}
double getDecimals( double dec ){
    return dec - (int)dec;
}
 
void main(){
    double dec = 1234.56789;
    printf( "\n%d", getDigitFromNum( (int)dec, 0 ));
    printf( "\n%d", getDigitFromDec( dec, 2 ));
    printf( "\n%f", getDecimals( dec ));
}

Output:

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0.567890

Code of the Day: Javascript Fibonacci Numbers the fast way

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//Programmer: Larry Battle
//Date: April 18, 2011
//Purpose: Get Fibonacci numbers in O(1) time.
var getFibonacciNum = function( n ){
    var s5 = Math.sqrt(5);
    var phi1 = (1+s5)/2, phi2 = (1-s5)/2;
    return Math.round((Math.pow( phi1, n ) - Math.pow( phi2, n) )/s5);
};

Demo:

Output for 0 to 4

F(0) = 0
F(1) = 1
F(2) = 1
F(3) = 2
F(4) = 3