Feat: add code export and import

[apoorvcodes]

Add some way to export or import codebases from other files for example

Export

export {
  foo
}

Import

import ( "src/export.monkey")

[skx]

That's an interesting idea, thanks for the suggestion.

I suspect I would not work on such a thing, but if you were willing to contribute I'd accept.

There are probably questions to be asked first though, like how this would affect scoping. The simple approach, like C using "include" would be easy to add, and could be done at the lexer/parser level:

#include "blah.monkey"

That works. But if you had an import like this:

import "time"

Where "time.monkey" had:

function today() { return "Monday"; }

Would that be called as today(), or time.today() ? Similarly how would you handle things that were public vs. private?

And finally would you need to support some kind of search-path, as used in perl/python?

[csd129]

The code below allows for monkey files to be imported, if you want play with or certainly improve.
So if a file, say foo.monkey contains

function today() { return "Monday"; }

It will be imported with
include("foo")

with the imported file being within the env var INCLUDEPATH or in the directory /usr/local/include/monkey or current directory.

The function would be called with today()

package evaluator

import (
	"os"
	"fmt"
	"strings"
	"monkey/object"
	"monkey/lexer"
	"monkey/parser"
)

func Include(env *object.Environment, args ...object.Object) object.Object {
	import_file:=args[0].Inspect()
	includes:=""
	if len(import_file) == 0 {
		return newError("ArgError: include() expects a file identifier, none given")
	}
	imp_filename:=fmt.Sprintf("%s.monkey", import_file)
	userincludes:=os.Getenv("INCLUDEPATH")
	if len(userincludes) == 0 {
		includes="/usr/local/include/monkey:."
	} else {
		includes=fmt.Sprintf("%s:%s", userincludes, "/usr/local/include/monkey:." )
	}
	incpaths:=strings.Split(includes, ":")
	for _, ipath := range incpaths {
		import_file=fmt.Sprintf("%s/%s", ipath, imp_filename)
		data, err := os.ReadFile(import_file)
		if err == nil {
			l := lexer.New(string(data))
			p := parser.New(l)
			program := p.ParseProgram()
			if len(p.Errors()) == 0 {
				Eval(program, env)
				return nil
			}
			fmt.Printf("Error parsing eval-string: %s", string(data))
			os.Exit(1)
		}
	}
	return newError("Unable to open file %s", imp_filename)
}

func init() {
	RegisterBuiltin("include",
		func(env *object.Environment, args ...object.Object) object.Object {
			return (Include(env, args...))
		})
}