Conditional assignment ?:

It''s a convenient replacement for a single if/else statement.
The real point is that it returns a value, while if/else doesn''t (directly).
I do use it extensively in my programs, I''m sure many do.

-Nik

the only time I use it is to replace statements like this

if(somecondition)
 y=something;
else
 y=somethingelse
 

with something like this

y = somecondition ? something : somethingelse;
 

you can definately get carried away with the conditional, but in this case, I think it''s justified.

You can use it in initializer lists, which is kind of cool. I saw that on here about two weeks ago or so.

edit: man I am tired.

[edited by - antareus on January 4, 2004 3:46:36 PM]

bah...

amateurs

// select array where we will perform search

const DXDeviceState *pSearchState = 
	(type == EDS_Render) ? m_pRenderStates
	: (type == EDS_Sampler) ? m_pSamplerStates
	: (type == EDS_Texture) ? m_pTextureStates
	: 0;
DWORD dwSearch = 
	(type == EDS_Render) ? m_dwNumRenderStates
	: (type == EDS_Sampler) ? m_dwNumSamplerStates
	: (type == EDS_Texture) ? m_dwNumTextureStates
	: 0;

ffx: I guarantee that's slower than the equivalent if-else lattice. I've written similar things before, and although they're ego-building, they're never faster or more readable once they get that complex. Just a note.

Later,
ZE.

//email me.//zealouselixir software.//msdn.//n00biez.//
miscellaneous links


[edited by - zealouselixir on January 4, 2004 3:59:34 PM]

Just some my old code. Damn things actually start to slow you down. Never use that kind of ?:

Here is assembly

1915:     // select array where we will perform search

1916:     const DXDeviceState *pSearchState =
1917:         (type == EDS_Render) ? m_pRenderStates
1918:         : (type == EDS_Sampler) ? m_pSamplerStates
1919:         : (type == EDS_Texture) ? m_pTextureStates
1920:         : 0;
10011A6E   cmp         dword ptr [type],1
10011A72   jne         Engine::CDirect3DEngine::CreateDeviceState+0BDh (10011a82)
10011A74   mov         ecx,dword ptr [this]
10011A77   mov         edx,dword ptr [ecx+2D4h]
10011A7D   mov         dword ptr [ebp-38h],edx
10011A80   jmp         Engine::CDirect3DEngine::CreateDeviceState+0F8h (10011abd)
10011A82   cmp         dword ptr [type],2
10011A86   jne         Engine::CDirect3DEngine::CreateDeviceState+0D1h (10011a96)
10011A88   mov         eax,dword ptr [this]
10011A8B   mov         ecx,dword ptr [eax+2D8h]
10011A91   mov         dword ptr [ebp-3Ch],ecx
10011A94   jmp         Engine::CDirect3DEngine::CreateDeviceState+0F2h (10011ab7)
10011A96   cmp         dword ptr [type],3
10011A9A   jne         Engine::CDirect3DEngine::CreateDeviceState+0E5h (10011aaa)
10011A9C   mov         edx,dword ptr [this]
10011A9F   mov         eax,dword ptr [edx+2DCh]
10011AA5   mov         dword ptr [ebp-40h],eax
10011AA8   jmp         Engine::CDirect3DEngine::CreateDeviceState+0ECh (10011ab1)
10011AAA   mov         dword ptr [ebp-40h],0
10011AB1   mov         ecx,dword ptr [ebp-40h]
10011AB4   mov         dword ptr [ebp-3Ch],ecx
10011AB7   mov         edx,dword ptr [ebp-3Ch]
10011ABA   mov         dword ptr [ebp-38h],edx
10011ABD   mov         eax,dword ptr [ebp-38h]
10011AC0   mov         dword ptr [pSearchState],eax
1921:     DWORD dwSearch =
1922:         (type == EDS_Render) ? m_dwNumRenderStates
1923:         : (type == EDS_Sampler) ? m_dwNumSamplerStates
1924:         : (type == EDS_Texture) ? m_dwNumTextureStates
1925:         : 0;
10011AC3   cmp         dword ptr [type],1
10011AC7   jne         Engine::CDirect3DEngine::CreateDeviceState+112h (10011ad7)
10011AC9   mov         ecx,dword ptr [this]
10011ACC   mov         edx,dword ptr [ecx+2E0h]
10011AD2   mov         dword ptr [ebp-44h],edx
10011AD5   jmp         Engine::CDirect3DEngine::CreateDeviceState+14Dh (10011b12)
10011AD7   cmp         dword ptr [type],2
10011ADB   jne         Engine::CDirect3DEngine::CreateDeviceState+126h (10011aeb)
10011ADD   mov         eax,dword ptr [this]
10011AE0   mov         ecx,dword ptr [eax+2E4h]
10011AE6   mov         dword ptr [ebp-48h],ecx
10011AE9   jmp         Engine::CDirect3DEngine::CreateDeviceState+147h (10011b0c)
10011AEB   cmp         dword ptr [type],3
10011AEF   jne         Engine::CDirect3DEngine::CreateDeviceState+13Ah (10011aff)
10011AF1   mov         edx,dword ptr [this]
10011AF4   mov         eax,dword ptr [edx+2E8h]
10011AFA   mov         dword ptr [ebp-4Ch],eax
10011AFD   jmp         Engine::CDirect3DEngine::CreateDeviceState+141h (10011b06)
10011AFF   mov         dword ptr [ebp-4Ch],0
10011B06   mov         ecx,dword ptr [ebp-4Ch]
10011B09   mov         dword ptr [ebp-48h],ecx
10011B0C   mov         edx,dword ptr [ebp-48h]
10011B0F   mov         dword ptr [ebp-44h],edx
10011B12   mov         eax,dword ptr [ebp-44h]
10011B15   mov         dword ptr [dwSearch],eax

Nasty ha...

quote:

---

Original post by ffx
bah...

amateurs

---

You realize thats a lot harder to read, right?

I'll use it whenever it applies. I used it in one of my programs for a class I'm taking at school where I had to delete a certain number of characters and I wanted to make sure it was positive so it looked like delete(x > 0 ? x : 0) and my teacher had never seen the operator before. Kind of scarry.

Edit: I've never used it like ffx showed, I only have one conditional. In that case I'd just use if statements. So far I've only used it on the right hand of an assignment and when passing an argument to a function.

[edited by - Aerolithe on January 4, 2004 4:34:03 PM]

?: is useful in obnoxiously scoped code segments. For example, member initializer lists, initialization of const variables, initialization of references and inside of macros where the block expansion of if/else would bork up expression/statement distinctions.

In reasonably complex code, I''d be somewhat suprised if I didn''t see at least one initializer list with a ?: inside and very suprised if I didn''t see at least one macro used with a ?: inside.