• Advertisement

Recommended Posts

Hi

heading is float alike 12.3524423

std::string sheading = std::to_string(heading);

now I only want to display 12.35

Many thanks in advance

 

Share this post


Link to post
Share on other sites
Advertisement

Or, if you don't mind using Boost, this:

	#include <iostream>
	#include <boost/format.hpp>
	#include <string>
	 
	int main()
	{
	  double x = 12.3524423;
	  std::string s = boost::str(boost::format("%.2f") % x);
	  std::cout << s << '\n';
	}

Share this post


Link to post
Share on other sites
7 hours ago, mike44 said:

Simple as:

sprintf(headingn,"%1.2f", heading);

That's simple, but also unsafe. How large is the buffer `headingn'? At the very least, you should use snprintf instead.

If you can avoid using C-style string manipulation, you are much less likely to introduce a buffer overflow in your program.

 

Share this post


Link to post
Share on other sites

Better thing is to cut it like that that should work

 

template <class type> type  TruncX(type x, int len)
{
	type denom = type(10.0);
	for (int i=0; i < len; i++)
		denom = denom * type(10.0);
return type(int(x*denom) / denom);
}

 

Share this post


Link to post
Share on other sites

Ok then ;p

inline AnsiString truncfstr(AnsiString text, AnsiString sign, int precision)
{
AnsiString s = text;
AnsiString tmp;
		tmp = stddelete(s,Pos(sign,s)+sign.length()+precision, 10000000);


return tmp;
}


inline int Pos(AnsiString sub, AnsiString str)
{
	 std::size_t found = str.find(sub,0);
	  if (found!=AnsiString ::npos)
		  return int(found)+1;
	  else
		  return 0;
}


inline AnsiString stddelete(AnsiString str, int pos, int len) //this is for AnsiString  only because i will call only Pos()-1 from it
{
	AnsiString s = str;
	 s.erase(pos, len);
	 return s;
}

Where typedef std::string AnsiString;

Should work

Share this post


Link to post
Share on other sites

Truncation like that is one way to do it, but most applications don't want that.

For an example, a value of 123.000001 that has a floating point rounding error beyond the value would be truncated to 123.00.  However, a value of 122.9999999 that has a rounding error below the intended value would unexpectedly go to 122.99 instead of the correct 123.00.

There are several different rounding modes. The ones typically used in computers (and supported by hardware) are:

  • Round to nearest, ties to even. This is also called "banker's rounding". 
  • Round to nearest, ties away from zero.
  • Round up
  • Round down
  • Round to zero, aka truncation.  This is the one you're doing.

The default mode -- which is also the version humans typically expect -- is the first.  

The programming language provides string manipulation functions that correctly round the value.  The printf family, the stream family precision functions, and Boost's string manipulation families all have the code to correctly round the result.  The first two are part of the language directly, there is no extra cost to use them. The Boost version is an extremely common library I've had available in most professional projects. They are already present and included in the code. Use the tools that are available to you.

Share this post


Link to post
Share on other sites
On 1/12/2018 at 10:30 PM, alvaro said:

Or, if you don't mind using Boost, this:

 

On this topic, Boost.Format is a header only library, so you don't need to add any libraries, dlls, etc to your project. 

Just note that Boost.Format is significantly slower than printf. That's not necessarily an issue (most applications don't spend all their time formatting strings), but just be aware of it.

Depending on your platform, you could also use Microsofts "secure" versions of sprintf

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Advertisement
  • Advertisement
  • Popular Tags

  • Advertisement
  • Popular Now

  • Similar Content

    • By francoisdiy
      So I wrote a programming language called C-Lesh to program games for my game maker Platformisis. It is a scripting language which tiles into the JavaScript game engine via a memory mapper using memory mapped I/O. Currently, I am porting the language as a standalone interpreter to be able to run on the PC and possibly other devices excluding the phone. The interpreter is being written in C++ so for those of you who are C++ fans you can see the different components implemented. Some background of the language and how to program in C-Lesh can be found here:

      http://www.codeloader.net/readme.html
      As I program this thing I will post code from different components and explain.
    • By isu diss
      I'm trying to duplicate vertices using std::map to be used in a vertex buffer. I don't get the correct index buffer(myInds) or vertex buffer(myVerts). I can get the index array from FBX but it differs from what I get in the following std::map code. Any help is much appreciated.
      struct FBXVTX { XMFLOAT3 Position; XMFLOAT2 TextureCoord; XMFLOAT3 Normal; }; std::map< FBXVTX, int > myVertsMap; std::vector<FBXVTX> myVerts; std::vector<int> myInds; HRESULT FBXLoader::Open(HWND hWnd, char* Filename, bool UsePositionOnly) { HRESULT hr = S_OK; if (FBXM) { FBXIOS = FbxIOSettings::Create(FBXM, IOSROOT); FBXM->SetIOSettings(FBXIOS); FBXI = FbxImporter::Create(FBXM, ""); if (!(FBXI->Initialize(Filename, -1, FBXIOS))) { hr = E_FAIL; MessageBox(hWnd, (wchar_t*)FBXI->GetStatus().GetErrorString(), TEXT("ALM"), MB_OK); } FBXS = FbxScene::Create(FBXM, "REALMS"); if (!FBXS) { hr = E_FAIL; MessageBox(hWnd, TEXT("Failed to create the scene"), TEXT("ALM"), MB_OK); } if (!(FBXI->Import(FBXS))) { hr = E_FAIL; MessageBox(hWnd, TEXT("Failed to import fbx file content into the scene"), TEXT("ALM"), MB_OK); } FbxAxisSystem OurAxisSystem = FbxAxisSystem::DirectX; FbxAxisSystem SceneAxisSystem = FBXS->GetGlobalSettings().GetAxisSystem(); if(SceneAxisSystem != OurAxisSystem) { FbxAxisSystem::DirectX.ConvertScene(FBXS); } FbxSystemUnit SceneSystemUnit = FBXS->GetGlobalSettings().GetSystemUnit(); if( SceneSystemUnit.GetScaleFactor() != 1.0 ) { FbxSystemUnit::cm.ConvertScene( FBXS ); } if (FBXI) FBXI->Destroy(); FbxNode* MainNode = FBXS->GetRootNode(); int NumKids = MainNode->GetChildCount(); FbxNode* ChildNode = NULL; for (int i=0; i<NumKids; i++) { ChildNode = MainNode->GetChild(i); FbxNodeAttribute* NodeAttribute = ChildNode->GetNodeAttribute(); if (NodeAttribute->GetAttributeType() == FbxNodeAttribute::eMesh) { FbxMesh* Mesh = ChildNode->GetMesh(); if (UsePositionOnly) { NumVertices = Mesh->GetControlPointsCount();//number of vertices MyV = new XMFLOAT3[NumVertices]; for (DWORD j = 0; j < NumVertices; j++) { FbxVector4 Vertex = Mesh->GetControlPointAt(j);//Gets the control point at the specified index. MyV[j] = XMFLOAT3((float)Vertex.mData[0], (float)Vertex.mData[1], (float)Vertex.mData[2]); } NumIndices = Mesh->GetPolygonVertexCount();//number of indices MyI = (DWORD*)Mesh->GetPolygonVertices();//index array } else { FbxLayerElementArrayTemplate<FbxVector2>* uvVertices = NULL; Mesh->GetTextureUV(&uvVertices); int idx = 0; for (int i = 0; i < Mesh->GetPolygonCount(); i++)//polygon(=mostly triangle) count { for (int j = 0; j < Mesh->GetPolygonSize(i); j++)//retrieves number of vertices in a polygon { FBXVTX myVert; int p_index = 3*i+j; int t_index = Mesh->GetTextureUVIndex(i, j); FbxVector4 Vertex = Mesh->GetControlPointAt(p_index);//Gets the control point at the specified index. myVert.Position = XMFLOAT3((float)Vertex.mData[0], (float)Vertex.mData[1], (float)Vertex.mData[2]); FbxVector4 Normal; Mesh->GetPolygonVertexNormal(i, j, Normal); myVert.Normal = XMFLOAT3((float)Normal.mData[0], (float)Normal.mData[1], (float)Normal.mData[2]); FbxVector2 uv = uvVertices->GetAt(t_index); myVert.TextureCoord = XMFLOAT2((float)uv.mData[0], (float)uv.mData[1]); if ( myVertsMap.find( myVert ) != myVertsMap.end() ) myInds.push_back( myVertsMap[ myVert ]); else { myVertsMap.insert( std::pair<FBXVTX, int> (myVert, idx ) ); myVerts.push_back(myVert); myInds.push_back(idx); idx++; } } } } } } } else { hr = E_FAIL; MessageBox(hWnd, TEXT("Failed to create the FBX Manager"), TEXT("ALM"), MB_OK); } return hr; } bool operator < ( const FBXVTX &lValue, const FBXVTX &rValue) { if (lValue.Position.x != rValue.Position.x) return(lValue.Position.x < rValue.Position.x); if (lValue.Position.y != rValue.Position.y) return(lValue.Position.y < rValue.Position.y); if (lValue.Position.z != rValue.Position.z) return(lValue.Position.z < rValue.Position.z); if (lValue.TextureCoord.x != rValue.TextureCoord.x) return(lValue.TextureCoord.x < rValue.TextureCoord.x); if (lValue.TextureCoord.y != rValue.TextureCoord.y) return(lValue.TextureCoord.y < rValue.TextureCoord.y); if (lValue.Normal.x != rValue.Normal.x) return(lValue.Normal.x < rValue.Normal.x); if (lValue.Normal.y != rValue.Normal.y) return(lValue.Normal.y < rValue.Normal.y); return(lValue.Normal.z < rValue.Normal.z); }  
    • By Karol Plewa
      Hi, 
       
      I am working on a project where I'm trying to use Forward Plus Rendering on point lights. I have a simple reflective scene with many point lights moving around it. I am using effects file (.fx) to keep my shaders in one place. I am having a problem with Compute Shader code. I cannot get it to work properly and calculate the tiles and lighting properly. 
       
      Is there anyone that is wishing to help me set up my compute shader?
      Thank you in advance for any replies and interest!
    • By fishyperil
      I'm looking for some references that could help me learn how to program some really basic 2D enemy behaviours.
      I wasn't sure whether to post this here or in the AI section but I think it might be more suitable to be posted here since it has more to do with basic maths than any AI related algorithms.
      Could anyone help recommend some resources (books, posts, videos) that could help me understand how to properly implement the basics of enemy movement in 2d games ? So far I've only managed to get them to chase the player character and to stop moving on collision, but the movement is pretty unrealistic and once the collision occurs the enemies all "pile up" on the player character. I'm doing this in C++ so no guides that explain how to script this using an engine api please.
    • By LifeArtist
      Good Evening,
      I want to make a 2D game which involves displaying some debug information. Especially for collision, enemy sights and so on ...
      First of I was thinking about all those shapes which I need will need for debugging purposes: circles, rectangles, lines, polygons.
      I am really stucked right now because of the fundamental question:
      Where do I store my vertices positions for each line (object)? Currently I am not using a model matrix because I am using orthographic projection and set the final position within the VBO. That means that if I add a new line I would have to expand the "points" array and re-upload (recall glBufferData) it every time. The other method would be to use a model matrix and a fixed vbo for a line but it would be also messy to exactly create a line from (0,0) to (100,20) calculating the rotation and scale to make it fit.
      If I proceed with option 1 "updating the array each frame" I was thinking of having 4 draw calls every frame for the lines vao, polygons vao and so on. 
      In addition to that I am planning to use some sort of ECS based architecture. So the other question would be:
      Should I treat those debug objects as entities/components?
      For me it would make sense to treat them as entities but that's creates a new issue with the previous array approach because it would have for example a transform and render component. A special render component for debug objects (no texture etc) ... For me the transform component is also just a matrix but how would I then define a line?
      Treating them as components would'nt be a good idea in my eyes because then I would always need an entity. Well entity is just an id !? So maybe its a component?
      Regards,
      LifeArtist
  • Advertisement