# Interview with Richard

### Fix the bugs in this function that converts a list of vectors into a list of points.

type Vector = {
    dx: number,
    dy; number,
};

type Point = {
    x: number,
    y: number,
};

/*
 * Convert an array of vectors into an array of points, starting
 * from (0,0), and in the same order as the array of vectors
 */
function makeAbs_(pts, v): Point[] {
    return [...pts, {
        x: pts[pts.length-1].x + v.dx,
        y: pts[pts.length-1].y + v.dy,
    }];
}
const makeAbsolute = (vs: Vector[]) =>
    vs.reduce(makeAbs_, [{x: 0, y: 0}]): Point[];

makeAbsolutes([{dx:1,dy:1},{dx:2,dy:2}])
 
 [{x:0, y:0}, {x:1,y:1}, {x:3,y:3}]
 
 makeAbs_([{x:3,y:3}, {x:1,y:1}], {dx:3,dy:3})
[{x:6,y;6},{x:3,y:3},{x:1,y:1}]
`
``typescript
[{x:1,y:1},{x:3,y:3}]

### Invert the case of a string.

Given a function to invert the case of a single character:

invertChar = (char: string): string =>
    char === char.toLowerCase() ? char.toUpperCase() : char.toLowerCase();

write a one-line function to invert the case of a string:

invertString = (str: string): string =>new String(str.toCharArray().map(invertChar));

### Why doesn't 0.4 + 0.8 == 1.2? (in javascript, Java, PHP, C, etc.)

proposed solutions:
* (abs(0.4+0.8 - 1.2) < 0.00001)
* round(0.4+0.8) == round(1.2)
* -- (sign)*(number)*2^(expontent)
* 10 * 0.4 + 10* 0.8 == 10 * 1.2

### If you could program in any language, what would it be?

* depends on application
* windows desktop: visual c++ (game, etc)
* website: servside language, php, java, scala
* desktop no graphics (could use C)
* mac: ObjC vs win: visual basic / visual c++ vs sunos: java

### Given an array of numbers, return the second greatest number without using sort.

var array = [0,3,5,1,8,6,4];

var greatest = -100000.0;

var secondgreatest = -100000.0;

var loopcounter = 0;

for( ; loopcounter < array.length; loopcounter = loopcounter + 1 ) {

    var currentvalue = array[ loopcounter ];

    var tempgreatest = -100000.0;

    //pick greatest
    if(currentvalue > greatest) {
        
        tempgreatest = greatest;
    
        greatest = currentvalue;    

    }
    //currentValue = 6
    //greatest = 8
    //secondgreatest = 5
    if(currentvalue > secondgreatest ) {
    
        if( secondgreatest < tempgreatest ) {

            secondgreatest = tempgreatest;

        }else if( currentvalue < greatest ) {
        
            secondgreatest = currentvalue;
        
        }
    
    }
    
}

### Discuss advantages vs disadvantages of (more complicated versions of)

const max = a > b ? a : b;

    vs.
    

const max = Math.max(a,b);

pros of writing it out:
* if you don't have the library available
* common idiom
* makes any side effects explicit
* program space
    * how much of the math library are you actually going to use?

pros of library use:
* more intuitive
* more english-like syntax, easier to read
* easier to refactor into a remote call
* reusability, consistant
* ease of refactoring