golox/interpreter/callable.go

package interpreter

import "golox/ast"

// callable is an interface for callables like functions and methods.
type callable interface {
	arity() int
	call(i *Interpreter, arguments []any) any
}

// nativeCallable is a struct that implements the callable interface.
type nativeCallable struct {
	arityFn func() int
	callFn  func(interpreter *Interpreter, args []any) any
}

// newNativeCallable creates a new nativeCallable.
func newNativeCallable(arityFn func() int, callFn func(interpreter *Interpreter, args []any) any) *nativeCallable {
	return &nativeCallable{
		arityFn: arityFn,
		callFn:  callFn,
	}
}

// arity returns the number of arguments the callable expects.
func (n *nativeCallable) arity() int {
	return n.arityFn()
}

// call calls the callable with the given arguments.
func (n *nativeCallable) call(i *Interpreter, arguments []any) any {
	return n.callFn(i, arguments)
}

// String returns a string representation of the callable.
func (n *nativeCallable) String() string {
	return "<native fn>"
}

// function is a struct that implements the callable interface.
type function struct {
	declaration *ast.FunctionStmt
}

// newFunction creates a new function.
func newFunction(declaration *ast.FunctionStmt) *function {
	return &function{
		declaration: declaration,
	}
}

// arity returns the number of arguments the function expects.
func (f *function) arity() int {
	return len(f.declaration.Params)
}

// call calls the function with the given arguments.
func (f *function) call(i *Interpreter, arguments []any) any {
	env := newEnvironment(i.globals)

	for i, param := range f.declaration.Params {
		env.define(param.Lexeme, arguments[i])
	}

	i.executeBlock(f.declaration.Body, env)

	return nil
}

// String returns a string representation of the function.
func (f *function) String() string {
	return "<fn " + f.declaration.Name.Lexeme + ">"
}