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Hello,

I sometimes use the following pattern:

static const struct {
    const char* name;
    void (*func)(int);
} functions[] = {
     { "function1", [](int) { ... } },
     { "function2", [](int) { ... } },
     ...
};

And when I look at the generated code, I see that this array gets generated
at runtime.

Ideally I would like to declare this array constexpr, and that would work
if I used named functions, however it does not for lambda, and I cannot see
any good reason for that.

As the function pointer conversion operator only exists for state-less
lambda, would'nt it make sense to define them as constexpr and their
conversion operator as well ?

Cheers,

Maxime Coste.

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<div dir=3D"ltr">Hello,<br><br>I sometimes use the following pattern:<br><b=
r><div class=3D"prettyprint" style=3D"background-color: rgb(250, 250, 250);=
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word-wrap: break-word;"><code class=3D"prettyprint"><div class=3D"subpretty=
print"><span style=3D"color: #008;" class=3D"styled-by-prettify">static</sp=
an><span style=3D"color: #000;" class=3D"styled-by-prettify"> </span><span =
style=3D"color: #008;" class=3D"styled-by-prettify">const</span><span style=
=3D"color: #000;" class=3D"styled-by-prettify"> </span><span style=3D"color=
: #008;" class=3D"styled-by-prettify">struct</span><span style=3D"color: #0=
00;" class=3D"styled-by-prettify"> </span><span style=3D"color: #660;" clas=
s=3D"styled-by-prettify">{</span><span style=3D"color: #000;" class=3D"styl=
ed-by-prettify"><br>&nbsp; &nbsp; </span><span style=3D"color: #008;" class=
=3D"styled-by-prettify">const</span><span style=3D"color: #000;" class=3D"s=
tyled-by-prettify"> </span><span style=3D"color: #008;" class=3D"styled-by-=
prettify">char</span><span style=3D"color: #660;" class=3D"styled-by-pretti=
fy">*</span><span style=3D"color: #000;" class=3D"styled-by-prettify"> name=
</span><span style=3D"color: #660;" class=3D"styled-by-prettify">;</span><s=
pan style=3D"color: #000;" class=3D"styled-by-prettify"><br>&nbsp; &nbsp; <=
/span><span style=3D"color: #008;" class=3D"styled-by-prettify">void</span>=
<span style=3D"color: #000;" class=3D"styled-by-prettify"> </span><span sty=
le=3D"color: #660;" class=3D"styled-by-prettify">(*</span><span style=3D"co=
lor: #000;" class=3D"styled-by-prettify">func</span><span style=3D"color: #=
660;" class=3D"styled-by-prettify">)(</span><span style=3D"color: #008;" cl=
ass=3D"styled-by-prettify">int</span><span style=3D"color: #660;" class=3D"=
styled-by-prettify">);</span><span style=3D"color: #000;" class=3D"styled-b=
y-prettify"><br></span><span style=3D"color: #660;" class=3D"styled-by-pret=
tify">}</span><span style=3D"color: #000;" class=3D"styled-by-prettify"> fu=
nctions</span><span style=3D"color: #660;" class=3D"styled-by-prettify">[]<=
/span><span style=3D"color: #000;" class=3D"styled-by-prettify"> </span><sp=
an style=3D"color: #660;" class=3D"styled-by-prettify">=3D</span><span styl=
e=3D"color: #000;" class=3D"styled-by-prettify"> </span><span style=3D"colo=
r: #660;" class=3D"styled-by-prettify">{</span><span style=3D"color: #000;"=
 class=3D"styled-by-prettify"><br>&nbsp; &nbsp; &nbsp;</span><span style=3D=
"color: #660;" class=3D"styled-by-prettify">{</span><span style=3D"color: #=
000;" class=3D"styled-by-prettify"> </span><span style=3D"color: #080;" cla=
ss=3D"styled-by-prettify">"function1"</span><span style=3D"color: #660;" cl=
ass=3D"styled-by-prettify">,</span><span style=3D"color: #000;" class=3D"st=
yled-by-prettify"> </span><span style=3D"color: #660;" class=3D"styled-by-p=
rettify">[](</span><span style=3D"color: #008;" class=3D"styled-by-prettify=
">int</span><span style=3D"color: #660;" class=3D"styled-by-prettify">)</sp=
an><span style=3D"color: #000;" class=3D"styled-by-prettify"> </span><span =
style=3D"color: #660;" class=3D"styled-by-prettify">{</span><span style=3D"=
color: #000;" class=3D"styled-by-prettify"> </span><span style=3D"color: #6=
60;" class=3D"styled-by-prettify">...</span><span style=3D"color: #000;" cl=
ass=3D"styled-by-prettify"> </span><span style=3D"color: #660;" class=3D"st=
yled-by-prettify">}</span><span style=3D"color: #000;" class=3D"styled-by-p=
rettify"> </span><span style=3D"color: #660;" class=3D"styled-by-prettify">=
},</span><span style=3D"color: #000;" class=3D"styled-by-prettify"><br>&nbs=
p; &nbsp; &nbsp;</span><span style=3D"color: #660;" class=3D"styled-by-pret=
tify">{</span><span style=3D"color: #000;" class=3D"styled-by-prettify"> </=
span><span style=3D"color: #080;" class=3D"styled-by-prettify">"function2"<=
/span><span style=3D"color: #660;" class=3D"styled-by-prettify">,</span><sp=
an style=3D"color: #000;" class=3D"styled-by-prettify"> </span><span style=
=3D"color: #660;" class=3D"styled-by-prettify">[](</span><span style=3D"col=
or: #008;" class=3D"styled-by-prettify">int</span><span style=3D"color: #66=
0;" class=3D"styled-by-prettify">)</span><span style=3D"color: #000;" class=
=3D"styled-by-prettify"> </span><span style=3D"color: #660;" class=3D"style=
d-by-prettify">{</span><span style=3D"color: #000;" class=3D"styled-by-pret=
tify"> </span><span style=3D"color: #660;" class=3D"styled-by-prettify">...=
</span><span style=3D"color: #000;" class=3D"styled-by-prettify"> </span><s=
pan style=3D"color: #660;" class=3D"styled-by-prettify">}</span><span style=
=3D"color: #000;" class=3D"styled-by-prettify"> </span><span style=3D"color=
: #660;" class=3D"styled-by-prettify">},</span><span style=3D"color: #000;"=
 class=3D"styled-by-prettify"><br>&nbsp; &nbsp; &nbsp;</span><span style=3D=
"color: #660;" class=3D"styled-by-prettify">...</span><span style=3D"color:=
 #000;" class=3D"styled-by-prettify"><br></span><span style=3D"color: #660;=
" class=3D"styled-by-prettify">};</span><span style=3D"color: #000;" class=
=3D"styled-by-prettify"><br></span></div></code></div><br>And when I look a=
t the generated code, I see that this array gets generated at runtime.<br><=
br>Ideally I would like to declare this array constexpr, and that would wor=
k if I used named functions, however it does not for lambda, and I cannot s=
ee any good reason for that.<br><br>As the function pointer conversion oper=
ator only exists for state-less lambda, would'nt it make sense to define th=
em as constexpr and their conversion operator as well ?<br><br>Cheers,<br><=
br>Maxime Coste.<br></div>

<p></p>

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/a>.<br />

------=_Part_298_4934272.1405533107174--

.

Yes, it should.  This would also allow lambdas to be used as function argument template parameters somewhat.

However nothing in C++ stops that array from being compile time initialized even if it is not constexpr.

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.