c++ - Ordered associative containers of pointers -


this question has answer here:

is okay practice define ordered associative containers of pointers (either built-in or class-type ones) despite fact that, far can tell standard, relational operators on (non-array objects et al.) pointers undefined?

from 5.9 of c++11 standard:

  1. if 2 pointers p , q of same type point different objects not members of same object or elements of same array or different functions, or if 1 of them null, results of p<q, p>q, p<=q, , p>=q unspecified.

since ordered containers (map, set, multimap , multiset) use < operator default provide total order compiles fine create set of pointers. again if relational operators pointers unspecified p<q , p>q both test false or true meaning may not idea ordering of set. would've accepted bad idea if wasn't fact example in book (c++ primer 5th ed chapter 13.4) defines set of pointers class type folder*, i.e. set<folder*> seemingly no comment on concern.

the ordered associative containers not use operator< directly, use std::less, defined , establishes total ordering pointer types, when operator< isn't.

so, fine instantiate std::set or std::map pointer types keys.


-

Comments

Post a Comment

Popular posts from this blog

c# - SharpDX Toolkit models rendering inside out -

a little while ago decided switch xna sharpdx toolkit actively being supported , quite similar xna. while i've had no trouble @ creating 2d games decided attempt basic 3d game. can both model , it's texture load when renders shows texture on side facing away camera doesn't show @ in between. this code using set environment. vector3 cameraposition = new vector3(0, 0, -10f * 2.5f); vector3 cameratarget = vector3.zero; boundingsphere modelbounds = model.calculatebounds(); float fovangle = mathutil.degreestoradians(45); float aspectratio = (float)graphicsdevice.backbuffer.width / graphicsdevice.backbuffer.height; float near = 0.01f; float far = 100f; float scaling = 10f / modelbounds.radius; matrix translation = matrix.scaling(scaling) * matrix.rotationy((float)gametime.totalgametime.totalseconds) * matrix.translation(0, -modelbounds.center.y * scaling, 0); matrix lookat = matrix.lookatlh(cameraposition, cameratarget, vector3.u...
Read more

c# - ajax - How to receive data both html and json from server? -

i have referenced this topic , doesn't solve problem. i'm using mvc 5 c#. have used code receive data server data type json . $.ajax({ url: "/mycontroller/myaction", type: "post", datatype: "json", success: function (data) { if (data.result) { alert('successfull'); } else { alert(data.ex); } } }); and controller code: [httppost] public actionresult myaction() { try { return json(new { result = "true", ex = "" }); } catch (exception e) { return json(new { result = "false", ex = e.message }); } } i use way data type html: $.ajax({ url: "/mycontroller/myaction", type: "post", datatype: "html", success: function (data) { $(".mydiv").append(data); } }); and controller should be: [httppost] public actionresult myaction() { return partialview("_...
Read more