construction_and_lifetime.md

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Construction & Lifetime

This page documents all ways to construct and manage the lifetime of a var object, using a clear tabular format with concise examples.

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Constructors

Constructor	Description	Example
var()	Default (int 0)	var a; // 0
var(NoneType{})	Pythonic None	var n(NoneType{}); // None
var(bool)	Boolean	var b(true); // true
var(int)	Integer	var i = 42; // 42
var(double)	Floating-point	var d = 3.14; // 3.14
var(const char*)	String	var s("hello"); // "hello"
var(const std::string&)	String	var s(std::string("hi")); // "hi"
var(List/Set/Dict/...)	Container types	var vlist(list(1,2,3));
graph(n)	Graph (VarGraph wrapper)	var vg = graph(5);

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Converter Helpers

Helper	Description	Example
Bool(v)	Convert to bool	Bool("abc") // true
Str(v)	Convert to string	Str(123)
String(v)	Convert to string	String(123)
Int(v)	Convert to int	Int("42")
Long(v)	Convert to long	Long("42")
LongLong(v)	Convert to long long	LongLong("42")
UInt(v)	Convert to unsigned int	UInt("42")
ULong(v)	Convert to unsigned long	ULong("42")
ULongLong(v)	Convert to unsigned long long	ULongLong("42")
Double(v)	Convert to double	Double("3.14")
Float(v)	Convert to float	Float("3.14")
LongDouble(v)	Convert to long double	LongDouble("3.14")
list(...)	Create List	list(1,2,3)
dict({...})	Create Dict	dict({{"a",1}})
set(...)	Create Set	set(1,2,3)
ordered_set(...)	Create OrderedSet	ordered_set(3,1,2)
ordered_dict({...})	Create OrderedDict	ordered_dict({{"k",1}})
graph(n)	Create Graph	graph(5)
load_graph(path)	Load Graph from file	load_graph("file")

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Input

Function	Description	Example
input(prompt="")	Read a line from standard input, optionally displaying a prompt	input("Enter value: ")

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Copy / Move Semantics

Operation	Description	Example
Copy constructor	Deep copy for heap types	var b = a;
Move constructor	Steals heap data if possible	var c = std::move(a);
Destructor	Frees heap-allocated contents	~var() (automatic)

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Examples

#include "pythonic/pythonic.hpp"
using namespace py;

// --- Direct Constructors ---
var a;                        // default -> 0
var n(NoneType{});            // None
var b(true);                  // bool
var i = 42;                   // int
var ui = static_cast<unsigned int>(123u); // unsigned int
var l = 123456789L;           // long
var ul = static_cast<unsigned long>(123456789UL); // unsigned long
var ll = 123456789012345LL;   // long long
var ull = static_cast<unsigned long long>(123456789012345ULL); // unsigned long long
var f = 3.14f;                // float
var d = 3.1415;               // double
var ld = (long double)1.23456789L; // long double
var s1("hello");             // const char*
var s2(std::string("world")); // std::string

// --- Container Constructors ---
List lst = { var(1), var(2), var(3) };
var vlist(lst);
Set st = { var(1), var(2), var(3) };
var vset(st);
Dict dct = {{"a", var(1)}, {"b", var(2)}};
var vdict(dct);
OrderedSet os = { var(3), var(1), var(2) };
var vos(os);
OrderedDict od = { {"k1", var(1)}, {"k2", var(2)} };
var vod(od);

// --- Graph Constructor ---
var vg = graph(5); // recommended
vg.add_edge(0, 1);
vg.save_graph("mygraph.txt"); // save the graph to a file

// --- Converter Helpers ---
var vstr = "123";
var vbool = Bool(vstr);         // true
var vint = Int(vstr);           // 123
var vlong = Long(vstr);         // 123L
var vll = LongLong(vstr);       // 123LL
var vuint = UInt(vstr);         // 123u
var vul = ULong(vstr);          // 123ul
var vull = ULongLong(vstr);     // 123ull
var vfloat = Float(vstr);       // 123.0f
var vdouble = Double(vstr);     // 123.0
var vld = LongDouble(vstr);     // 123.0L
var vstr2 = Str(vint);          // "123"
var vstr3 = String(vint);       // "123"

// --- Factory Helpers ---
var flist = list(1, 2, 3);
var fset = set(1, 2, 3);
var fodset = ordered_set(3, 1, 2);
var fdict = dict({{"a", 1}, {"b", 2}});
var fodict = ordered_dict({{"k1", 1}, {"k2", 2}});
var fgraph = graph(5);
var loaded = load_graph("mygraph.txt"); // load the graph from the file
//auto loaded = load_graph("/path/to/graph.file");


// --- input ---
 var user_input = input("Enter value: ");

// --- Copy / Move / Destructor ---
var copy = flist;               // copy
var moved = std::move(flist);   // move

// --- Output ---
print(a, n, b, i, ui, l, ul, ll, ull, f, d, ld, s1, s2);
print(vlist); print(vset); print(vdict); print(vos); print(vod); print(vg);
print(vbool, vint, vlong, vll, vuint, vul, vull, vfloat, vdouble, vld, vstr2, vstr3);
print(flist, fset, fodset, fdict, fodict, fgraph, loaded);
print(copy, moved);

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Notes

• Use constructors for direct value storage.
• Use converter helpers for explicit conversion or factory creation.
• Prefer move for large containers to avoid unnecessary copies.
• All containers and graphs are stored as heap-backed types inside var.

Next check

• Type Introspection & Conversion