ChaiScript tries to follow the Semantic Versioning scheme. This basically means:
- Major Version Number: API changes / breaking changes
- Minor Version Number: New Features
- Patch Version Number: Minor changes / enhancements
chaiscript::ChaiScript chai; // loads stdlib from loadable module on file system
chaiscript::ChaiScript chai(chaiscript::Std_Lib::library()); // compiles in stdlib
chai.add(chaiscript::fun(&function_name), "function_name");
chai.add(chaiscript::fun(&Class::method_name), "method_name");
chai.add(chaiscript::fun(&Class::member_name), "member_name");
chai.add(chaiscript::fun<ReturnType (ParamType1, ParamType2)>(&function_with_overloads), "function_name");
chai.add(chaiscript::fun(std::static_cast<ReturnType (*)(ParamType1, ParamType2)>(&function_with_overloads)), "function_name");
This overload technique is also used when exposing base member using derived type
struct Base
{
int data;
};
struct Derived : public Base
{};
chai.add(chaiscript::fun(static_cast<int(Derived::*)>(&Derived::data)), "data");
chai.add(
chaiscript::fun<std::string (bool)>(
[](bool type) {
if (type) { return "x"; }
else { return "y"; }
}), "function_name");
chai.add(chaiscript::constructor<MyType ()>(), "MyType");
chai.add(chaiscript::constructor<MyType (const MyType &)>(), "MyType");
It's not strictly necessary to add types, but it helps with many things. Cloning, better errors, etc.
chai.add(chaiscript::user_type<MyClass>(), "MyClass");
User defined type conversions are possible, defined in either script or in C++.
A helper function exists for strongly typed and ChaiScript Vector function conversion definition:
chai.add(chaiscript::vector_conversion<std::vector<int>>());
This allows you to pass a ChaiScript function to a function requiring std::vector<int>
chai.add(chaiscript::var(somevar), "somevar"); // copied in
chai.add(chaiscript::var(std::ref(somevar), "somevar"); // by reference, shared between C++ and chai
auto shareddouble = std::make_shared<double>(4.3);
chai.add(chaiscript::var(shareddouble), "shareddouble"); // by shared_ptr, shared between c++ and chai
chai.add(chaiscript::const_var(somevar), "somevar"); // copied in and made const
chai.add_global_const(chaiscript::const_var(somevar), "somevar"); // global const. Throws if value is non-const
chai.add_global(chaiscript::var(somevar), "somevar"); // global non-const
ChaiScript recognize many types from STL, but you have to add specific instantiation yourself.
typedef std::vector<std::pair<int, std::string>> data_list;
data_list my_list{ make_pair(0, "Hello"), make_pair(1, "World") };
chai.add(chaiscript::bootstrap::standard_library::vector_type<data_list>("DataList"));
chai.add(chaiscript::bootstrap::standard_library::pair_type<data_list::value_type>("DataElement"));
chai.add(chaiscript::var(&my_list), "data_list");
chai.eval(R"_(
for(var i=0; i<data_list.size(); ++i)
{
print(to_string(data_list[i].first) + " " + data_list[i].second)
}
)_");
chai.eval("print(\"Hello World\")");
chai.eval(R"(print("Hello World"))");
Returns values are of the type Boxed_Value which is meant to be opaque to the programmer. Use one of the unboxing methods to access the internal data.
chai.eval<double>("5.3 + 2.1"); // returns 7.4 as a C++ double
auto v = chai.eval("5.3 + 2.1");
chai.boxed_cast<double>(v); // extracts double value from boxed_value and applies known conversions
chaiscript::boxed_cast<double>(v); // free function version, does not know about conversions
chaiscript::Boxed_Number(chai.eval("5.3 + 2.1")).get_as<int>(); // works with any number type
// which is equivalent to, but much more automatic than:
static_cast<int>(chai.eval<double>("5.3+2.1")); // this version only works if we know that it's a double
double &d = chai.eval("var i = 5.2; i"); // d is now a reference to i in the script
std::shared_ptr<double> d = chai.eval("var i = 5.2; i"); // same result but reference counted
d = 3;
chai.eval("print(i)"); // prints 3
try {
chai.eval("2.3 + \"String\"");
} catch (const chaiscript::exception::eval_error &e) {
std::cout << "Error\n" << e.pretty_print() << '\n';
}
try {
chai.eval("throw(runtime_error(\"error\"))", chaiscript::exception_specification<int, double, float, const std::string &, const std::exception &>());
} catch (const double e) {
} catch (int) {
} catch (float) {
} catch (const std::string &) {
} catch (const std::exception &e) {
// This is the one what will be called in the specific throw() above
}
auto p = chai.eval<std::function<std::string (double)>>("to_string");
p(5); // calls chaiscript's 'to_string' function, returning std::string("5")
Note: backtick treats operators as normal functions
auto p = chai.eval<std::function<int (int, int)>>(`+`);
p(5, 6); // calls chaiscript's '+' function, returning 11
auto p = chai.eval<std::function<std::string (int, double)>>("fun(x,y) { to_string(x) + to_string(y); }");
p(3,4.2); // evaluates the lambda function, returning the string "34.2" to C++
var i; // uninitialized variable, can take any value on first assignment;
auto j; // equiv to var
var k = 5; // initialized to 5 (integer)
var l := k; // reference to k
auto &m = k; // reference to k
GLOBAL g = 5; // creates a global variable. If global already exists, it is not re-added
GLOBAL g = 2; // global 'g' now equals 2
GLOBAL g2;
if (g2.is_var_undef()) { g2 = 4; } // only initialize g2 once, if GLOBAL decl hit more than once
var v = [1,2,3u,4ll,"16", `+`]; // creates vector of heterogenous values
var m = ["a":1, "b":2]; // map of string:value pairs
Floating point values default to double type and integers default to int type. All C++ suffixes
such as f, ll, u as well as scientific notation are supported
1.0 // double
1.0f // float
1.0l // long double
1 // int
1u // unsigned int
1ul // unsigned long
1ull // unsigned long long
Literals are automatically sized, just as in C++. For example: 10000000000 is > 32bits and the appropriate type is used to hold it
on your platform.
Note that any type of ChaiScript function can be passed freely to C++ and automatically
converted into an std::function object.
def myfun(x, y) { x + y; } // last statement in body is the return value
def myfun(x, y) { return x + y; } // equiv
def myfun(x, int y) { x + y; } // requires y to be an int
def myfun(x, int y) : y > 5 { x - y; } // only called if y > 5
Methods and functions are mostly equivalent
def string::add(int y) { this + to_string(y); }
def add(string s, int y) { s + to_string(y); } //equiv functionality
// calling new function/method
"a".add(1); // returns a1
add("a", 1); // returns a1, either calling syntax works with either def above
var l = fun(x) { x * 15; }
l(2) // returns 30
var a = 13
var m = fun[a](x) { x * a; }
m(3); // a was captured (by reference), returns 39
var n = bind(fun(x,y) { x * y; }, _, 10);
n(2); // returns 20
Define a type called "MyType" with one member value "a" and a getter
class MyType {
var value;
def MyType() { this.value = "a"; }
def get_value() { "Value Is: " + this.value; }
};
attr MyType::value;
def MyType::MyType() { this.value = "a"; }
def MyType::get_value() { "Value Is: " + this.value; }
var m = MyType(); // calls constructor
print(m.get_value()); // prints "Value Is: a"
print(get_value(m)); // prints "Value Is: a"
All ChaiScript defined types and generic Dynamic_Object support dynamic parameters
var o = Dynamic_Object();
o.f = fun(x) { print(x); }
o.f(3); // prints "3"
Implicit 'this' is allowed:
var o = Dynamic_Object();
o.x = 3;
o.f = fun(y) { print(this.x + y); }
o.f(10); // prints 13
If you want to disable dynamic parameter definitions, you can set_explicit.
class My_Class {
def My_Class() {
this.set_explicit(true);
this.x = 2; // this would fail with explicit set to true
}
};
A function of the signature method_missing(object, name, param1, param2, param3) will be called if an appropriate
method cannot be found
def method_missing(int i, string name, Vector v) {
print("method_missing(${i}, ${name}), ${v.size()} params");
}
5.bob(1,2,3); // prints "method_missing(5, bob, 3 params)"
method_missing signature can be either 2 parameters or 3 parameters. If the signature contains two parameters
it is treated as a property. If the property contains a function then additional parameters are passed to
the contained function.
If both a 2 parameter and a 3 parameter signature match, the 3 parameter function always wins.
eval("4 + 5") // dynamically eval script string and returns value of last statement
eval_file("filename") // evals file and returns value of last statement
use("filename") // evals file exactly once and returns value of last statement
// if the file had already been 'used' nothing happens and undefined is returned
Both use and eval_file search the 'usepaths' passed to the ChaiScript constructor