[Help] debug template for ICPC

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I am unfortunately not very good at writing code and can barely function without an easy way to debug said code. I therefore need a debug template at ICPC and spent some time reducing the length of the debug template I use normally. I think it's pretty short already, but it seems like it can be shortened further. I don't know how to do so, hence this blog.

Some considerations:

Can only use features introduced in C++ 17 or earlier, as my region is weird.
Need to be able to debug all STL containers, and any nested versions thereof.

Now, if C++ 20 were allowed, one could simply use the following:

Code

template<typename T> 
void __print(const T& x) {
    if constexpr (is_arithmetic_v<T> or is_same_v<T, string>) cerr << x;
    else {
        cerr << '{';
        if constexpr (requires {x.first;})
            __print(x.first), cerr << ", ", __print(x.first);
        else {
            int f = 0; for(auto i : x) cerr << (f ++ ? ", " : ""), __print(i);}
        cerr << '}';
    }
}
template <typename... A>
void _print(const A&... a) {((__print(a), cerr << ", "), ...);}
#define debug(...) cerr << "[" << #__VA_ARGS__ << "] = ["; _print(__VA_ARGS__); cerr << "]\n";

__print() works by repeatedly considering the elements that constitute x and calling __print() on them (whilst ensuring that the output of each __print() call is separated by ,) until << is defined for x by default.

Now, what's the problem with making this code compatible with C++17?

The problem is that there doesn't seem to be a short (in terms of code length) way in C++17 to differentiate between pairs and iterable containers.

I found two solutions, both of which aren't good at all:

1) Use `is_literal_type_v` to check if `T` is a pair

Code

template<typename T> 
void __print(const T& x) {
    if constexpr (is_arithmetic_v<T> or is_same_v<T, string>) cerr << x;
    else {
        cerr << '{';
        if constexpr (is_literal_type_v<T>)
            __print(x.first), cerr << ", ", __print(x.second);
        else {
            int f = 0; for(auto i : x) cerr << (f ++ ? ", " : ""), __print(i);}
        cerr << '}';
    }
}
template <typename... A>
void _print(const A&... a) {((__print(a), cerr << ", "), ...);}
#define debug(...) cerr << "[" << #__VA_ARGS__ << "] = ["; _print(__VA_ARGS__); cerr << "]\n";

This will work if we have pairs like std::pair<int, float> but not with something like std::pair<int, vector<int>>. This is a significant loss of functionality since we now cannot debug things like map<int, vector<int>> which are often used.

2) Just create a separate templated function for pairs

Code

struct {
    template<typename T> 
    void __print(const T& x) {
        if constexpr (is_arithmetic_v<T> or is_same_v<T, string>)   cerr << x;
        else {
            cerr << '{';
            int f = 0; for(auto i : x) cerr << (f ++ ? ", " : ""), __print(i);
            cerr << '}';
        }
    }
    template<typename X, typename Y>
    void __print(const pair<X, Y>& x){
        cerr << '{', __print(x.first), cerr << ", ", __print(x.second), cerr << '}';
    }
    template <typename... A>
    void _print(const A&... a) {((__print(a), cerr << ", "), ...);}
}_d;
#define debug(...) cerr << "[" << #__VA_ARGS__ << "] = ["; _d._print(__VA_ARGS__); cerr << "]\n";

This is also bad because:

Much longer code.
Notice that we now need to use a class/struct/namespace for the two __print() functions as they can call each other.

Can someone help me fix these issues and/or make the code shorter in general? Right now, I think the last one is the best. I can't believe I spent the last 3 hours shortening a piece of code by 5 lines.

For whatever reason, GPT and Claude seems to be unhelpful here. I ran out of access to 4o trying to get it to help me, despite purchasing GPT plus T_T

string to_string(string s) { return '"' + s + '"'; } string to_string(const char* s) { return to_string((string) s); } string to_string(bool b) { return (b ? "true" : "false"); } template <typename A, typename B> string to_string(pair<A, B> p) { return "(" + to_string(p.first) + ", " + to_string(p.second) + ")"; } template <typename A> string to_string(A v) { bool first = true; string res = "{"; for (const auto &x : v) { if (!first) { res += ", "; } first = false; res += to_string(x); } res += "}"; return res; } void debug_out() { cerr << endl; } template <typename Head, typename... Tail> void debug_out(Head H, Tail... T) { cerr << " " << to_string(H); debug_out(T...); }

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unalive

2 дня назад, # |