representation

问题 I notice that a lot of drawing APIs have their 0,0 origin at the top left corner, so y actually goes down as it increases. I wonder why is that? Any particular advantage to not working in what I personally consider to be more logical bottom left corner (the origin of a regular x/y grid), which also happens to be the native representation of coordinates in hardware rendering APIs? Or maybe it has something to do with the way scanline rendering or even display refresh goes? 回答1: 2D raster

问题 In Octave I obtain 1 - 0.05 -0.95 = 0 and 1 - 0.95 -0.05 = 4.1633e-17 I understand that it is caused by the order of evaluation combined with the approximate binary representation of 0.05 as 0.00(0011) and 0.95 as 0.11(1100) Could someone please give me the whole story or show me a link explaining it? ---EDIT: This question is not a duplicate of Why is 24.0000 not equal to 24.0000 in MATLAB?, which was identified by others as a possible duplicate. The latter deals with the rounded

问题 My current project requires extensive use of bit fields. I found a simple, functional recipe for bit a field class but it was lacking a few features I needed, so I decided to extend it. I've just got to implementing __str__ and __repr__ and I want to make sure I'm following convention. __str__ is supposed to be informal and concice, so I've made it return the bit field's decimal value (i.e. str(bit field 11) would be "3" . __repr__ is supposed to be a official representation of the object, so

问题 If someone writes a class in python, and fails to specify their own __repr__() method, then a default one is provided for them. However, suppose we want to write a function which has the same, or similar, behavior to the default __repr__() . However, we want this function to have the behavior of the default __repr__() method even if the actual __repr__() for the class was overloaded. That is, suppose we want to write a function which has the same behavior as a default __repr__() regardless of

问题 I know that methods __repr__ and __str__ exist to give a formal and informal representation of class instances. But does an equivalent exist for class objects too, so that when the class object is printed, a nice representation of it could be shown? >>> class Foo: ... def __str__(self): ... return "instance of class Foo" ... >>> foo = Foo() >>> print foo instance of class Foo >>> print Foo __main__.Foo 回答1: When you call print(foo) , foo 's __str__ method is called. __str__ is found in the

问题 Is there a Matlab function that returns the binary representation of a float number? 回答1: In Matlab, one can use Java JDK functions. The short answer for converting float (single precision 32-bit number) in Matlab to a binary string representation might be: flt=3.14 import java.lang.Integer java.lang.Float; Integer.toBinaryString(Float.floatToIntBits(flt)) The long answer: conversion of float (single precision 32-bit number) in Matlab to a binary string representation function out

问题 Is there a Matlab function that returns the binary representation of a float number? 回答1: In Matlab, one can use Java JDK functions. The short answer for converting float (single precision 32-bit number) in Matlab to a binary string representation might be: flt=3.14 import java.lang.Integer java.lang.Float; Integer.toBinaryString(Float.floatToIntBits(flt)) The long answer: conversion of float (single precision 32-bit number) in Matlab to a binary string representation function out

问题 db.define_table('person', Field('name'), format='%(name)s') What does this format do here? 回答1: The format argument is used to determine how fields in other tables that reference the 'person' table will be displayed. For example, if you define: db.define_table('dog', Field('name'), Field('owner', db.person) The 'owner' field is a reference field that references the 'person' table (i.e., it stores record id's of records from the 'person' table). In most cases, when you display data from the

问题 I'm having trouble understanding how values of boxed traits come into existence. Consider the following code: trait Fooer { fn foo(&self); } impl Fooer for i32 { fn foo(&self) { println!("Fooer on i32!"); } } fn main() { let a = Box::new(32); // works, creates a Box<i32> let b = Box::<i32>::new(32); // works, creates a Box<i32> let c = Box::<Fooer>::new(32); // doesn't work let d: Box<Fooer> = Box::new(32); // works, creates a Box<Fooer> let e: Box<Fooer> = Box::<i32>::new(32); // works,

问题 How does a .NET decimal type get represented in binary in memory? We all know how floating-point numbers are stored and the thusly the reasons for the inaccuracy thereof, but I can't find any information about decimal except the following: Apparently more accurate than floating-point numbers Takes 128 bits of memory 2^96 + sign range 28 (sometimes 29?) total significant digits in the number Is there any way I can figure this out? The computer scientist in me demands the answer and after an