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PODoes "math.floor(x)" and "int(x)" produce different results for positive real numbers in Python?
 

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  1. PODoes "math.floor(x)" and "int(x)" produce different results for positive real numbers in Python?
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    <p>I have checked a few examples on the Python shell and they seem to spit out same numbers. But in a program where large set of numbers are supposed to be approximated, they apparently produce different results.</p> <p>I am trying to write a little program that simulates movement of an object on a rectangular plane. For that, I had to write a class named "RectangularRoom" that takes in a width and a height and creates a grid:</p> <pre><code>class RectangularRoom(object): """ A RectangularRoom represents a rectangular region containing clean or dirty tiles. A room has a width and a height and contains (width * height) tiles. At any particular time, each of these tiles is either clean or dirty. """ def __init__(self, width, height): """ Initializes a rectangular room with the specified width and height. Initially, no tiles in the room have been cleaned. width: an integer &gt; 0 height: an integer &gt; 0 """ self.width = width self.height = height self.room_coordinates = [] for m in range(self.width): for n in range(self.height): self.room_coordinates.append((m,n)) self.cleaned = [] def cleanTileAtPosition(self, pos): """ Mark the tile under the position POS as cleaned. Assumes that POS represents a valid position inside this room. pos: a Position """ self.cleaned.append((int(pos.getX()), int(pos.getY()))) def isTileCleaned(self, m, n): """ Return True if the tile (m, n) has been cleaned. Assumes that (m, n) represents a valid tile inside the room. m: an integer n: an integer returns: True if (m, n) is cleaned, False otherwise """ assert type (m)== int and type (n) == int return (m,n) in self.cleaned def getNumTiles(self): """ Return the total number of tiles in the room. returns: an integer """ return self.width*self.height def getNumCleanedTiles(self): """ Return the total number of clean tiles in the room. returns: an integer """ return len(self.cleaned) def getRandomPosition(self): """ Return a random position inside the room. returns: a Position object. """ return Position (random.randrange(0 , self.width), random.randrange(0 , self.height)) def isPositionInRoom(self, pos): """ Return True if pos is inside the room. pos: a Position object. returns: True if pos is in the room, False otherwise. """ return (int(pos.getX()), int(pos.getY())) in self.room_coordinates </code></pre> <p>As you see I implemented it using the int() method and the random generator "random.randrange".</p> <p>In the solution, the teacher has implemented this class using the math.floor() function and the random generator random.random():</p> <pre><code>class RectangularRoom(object): """ A RectangularRoom represents a rectangular region containing clean or dirty tiles. A room has a width and a height and contains (width * height) tiles. At any particular time, each of these tiles is either clean or dirty. """ def __init__(self, width, height): """ Initializes a rectangular room with the specified width and height. Initially, no tiles in the room have been cleaned. width: an integer &gt; 0 height: an integer &gt; 0 """ self.width = width self.height = height self.tiles = {} for x in range(self.width): for y in range(self.height): self.tiles[(x, y)] = False def cleanTileAtPosition(self, pos): """ Mark the tile under the position POS as cleaned. Assumes that POS represents a valid position inside this room. pos: a Position """ x = math.floor(pos.getX()) y = math.floor(pos.getY()) self.tiles[(x, y)] = True def isTileCleaned(self, m, n): """ Return True if the tile (m, n) has been cleaned. Assumes that (m, n) represents a valid tile inside the room. m: an integer n: an integer returns: True if (m, n) is cleaned, False otherwise """ return self.tiles[(m, n)] def getNumTiles(self): """ Return the total number of tiles in the room. returns: an integer """ return self.width * self.height def getNumCleanedTiles(self): """ Return the total number of clean tiles in the room. returns: an integer """ return sum(self.tiles.values()) def getRandomPosition(self): """ Return a random position inside the room. returns: a Position object. """ return Position(random.random() * self.width, random.random() * self.height) def isPositionInRoom(self, pos): """ Return True if pos is inside the room. pos: a Position object. returns: True if pos is in the room, False otherwise. """ return ((0 &lt;= pos.getX() &lt; self.width) and (0 &lt;= pos.getY() &lt; self.height)) </code></pre> <p>Surprisingly, these two chunks of code produce completely different results. I want to know why this happens. int() and floor() should have the same effect on a positive number and the two random functions seem to produce similar numbers.</p>
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