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POSimulate generic/templated lambdas on C++11
 

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  1. POSimulate generic/templated lambdas on C++11
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    <p>I got a problem on where I have something like this:</p> <pre><code>#define A_BODY printf("b is %s and c is %d, typeless! :3\n", b, c); #define B_BODY return "test"; #define C_BODY return 42; </code></pre> <p>I need to make a code that would, for example, call a(b(), c()), with their respective types.</p> <p>On C++14 I can easely do this:</p> <pre><code>template&lt;typename B, typename C&gt; auto a(B &amp;&amp;b, C &amp;&amp;c) { A_BODY }; auto b() { B_BODY }; auto c() { C_BODY }; int main() { auto _b = b(); auto _c = c(); auto _a = a(_b, _c); return 0; }; </code></pre> <p>Achieving the desired result... is there any way to get the same result on C++11? :'(</p> <p>Also, they can call each other recursively, so a simple ordering here wouldn't help either.</p> <h1>Edit</h1> <p>I will try to explain better my situation.</p> <p>I got an input file like this, for example:</p> <pre><code>a is b c { printf("b is %s and c is %d\n", b, c); if(c &gt; 42) printf("c is bigger than the truth!\n"); return strlen(b) + c; }; b is { return "test"; }; c is { return 42; }; </code></pre> <p>And I need to generate a C++ code that can properly call them. I'm trying to infer the return types without needing to define them on the input file.</p> <p>From that, I can get the <code>*_BODY</code> specifications, the number of parameters, and the order of calls, but I don't know which type the parameters will be. So I'd need an templated lambda, for example, to do lazy evaluation of the function body.</p> <p>I can do this with C++14 on GCC and CLang, but this is a commercial project and I need to support Visual Studio 2012 as well. I'm trying to find a workaround, if there is any. :(</p>
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    1. USpaulotorrens
    1. USpaulotorrens
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    1. COSince `b` must be `char const *` and c` must be `int`, maybe this example isn't the most representative of your problem?
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      1. USKerrek SB
    2. COThe thing is that `b` could be something different from `const char *`. This code should run on a **generated file**, thus `A_BODY`, `B_BODY`, `C_BODY`, and etc, could have any return types. The only thing is that some are parameters to others. Just consider that it should work with any return types on the `*_BODY`.
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      1. POSimulate generic/templated lambdas on C++11
      1. USpaulotorrens
    3. COHm, but if `b` is anything different, then your `A_BODY` is UB :-S
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      1. POSimulate generic/templated lambdas on C++11
      1. USKerrek SB
 

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