format.cpp

#include <iostream>
#include <cstdio>
#include <string>
#include <functional>
#include <cmath>
#include <initializer_list>

/*

Format("{type} {name} = -2*{pi}*sqrt(element)*pow({weights},2)", 
 Parameter("type") = data_type, 
 Parameter("name") = "outer_factor",
 Parameter("pi") = pi,
 Parameter("weights") = 0.6);
 
 output = float outer_factor=-2*3.1415+sqrt(element)*pow(0.6, 2);
*/

struct Parameter {
	
	Parameter(const char* name) : m_name(name) {}

	template <typename T>
	Parameter& operator=(const T& value) {
		cast = [&value]() { return std::to_string(value); };
		return *this;
	}

	Parameter& operator=(const char* value) {
		cast = [&value]() { return std::string(value); };
		return *this;
	}

	Parameter& operator=(std::string value) {
		cast = [&value]() { return value; };
		return *this;
	}

	operator std::string() const {
		return cast();
	}

	std::function <std::string()> cast;
	std::string m_name;
};

// ripped from http://stackoverflow.com/questions/2896600/how-to-replace-all-occurrences-of-a-character-in-string
std::string replace_all(std::string str, const std::string& from, const std::string& to) {
	size_t start_pos = 0;
    	while ((start_pos = str.find(from, start_pos)) != std::string::npos) {
        	str.replace(start_pos, from.length(), to);
        	start_pos += to.length(); // Handles case where 'to' is a substring of 'from'
    	}
    return str;
}

std::string format(const char* str, std::initializer_list<Parameter> params) {
	std::string fmt(str);
	std::cout << fmt << std::endl;
	for (auto i = params.begin(); i != params.end(); ++i) {
		fmt = replace_all(fmt, "{" + i->m_name + "}", *i);
	}
	return fmt;
}

int main() {
	float weights = 0.6;
	
	std::string s = Parameter("weights") = weights;
	std::cout << s << std::endl;
	
	s = Parameter("pi") = M_PI;
	std::cout << s << std::endl;

	s = Parameter("type") = "float";
	std::cout << s << std::endl;
	
	const char name[] = "double";
	s = Parameter("type") = name;
	std::cout << s << std::endl;
	
	std::string name_s("int");
	s = Parameter("type") = name_s;
	std::cout << s << std::endl;

	s = Parameter("val") = 1024;
	std::cout << s << std::endl;
	
	std::string fmt = format("{type1} {name_2} = -2*{pi_m}*sqrt(element)*pow({weights},2);", 
		{ 
			Parameter("type1") = "float", 
			Parameter("name_2") = "outer_factor", 
			Parameter("pi_m") = M_PI, 
			Parameter("weights") = weights
		} );
		
	std::cout << fmt << std::endl;

	return 0;
}

format.output

Success	time: 0 memory: 3236 signal:0
0.600000
3.141593
float
double
int
1024
{type1} {name_2} = -2*{pi_m}*sqrt(element)*pow({weights},2);
float outer_factor = -2*3.141593*sqrt(element)*pow(0.600000,2);