Question

You're given the type length = In of float | Cm of float. Write an OCaml function addlen(x,y) that adds two lengths. If x is in inches, the sum should be in inches; if x is in centimeters, the sum should be in centimeters. (Reminder: 2.54 cm per inch.)

Answer 1

First of, float is a datatype like any other available (like Int, Char, Double etc.).

Int = Integer (e.g. 4 or 10)

Float = Floating number up to 7 decimals (e.g. 1.0054 or 10.55555)

Double = Is also a floating number but up to 2 times larger: up to 15 or 16 decimals. (e.g. 1.5353415335)

Char = A Character (e.g. 'a' or 'G').

These are the most popular datatypes.

What you want to do in some programming languages like Objective-C in this case; is to tell the compiler what type the variable will have. If you're going to give the variable x = 1 then you must tell the compiler before you do that. You will need to change to declaration to: int x = 1. The same rules follows with the float and other datatypes.

An argument to a function is like Math in high-school. (example):

f(x) = 5x + 1.

or

f(x,y) = x + y.

The last function take two arguments: x and y.

The same logic is used in programming except that you tell the compiler what type the function will return.

f(x,y) = x + y

Will be in C-programming if you use Integers:

int f(int x, int y) { return x + y }

Your answer will probably be:

(in C):

float addTwo(float first, float second) {

    return first + second;

}

(in Objective-C):

- (float)addTwo:(float)first secondArgument:(float)second  {

    return first + second;

}