added

vendor/github.com/glycerine/zygomys/zygo/import.go

@@ -0,0 +1,67 @@
+package zygo
+
+import (
+	"fmt"
+)
+
+// import a package, analagous to Golang.
+func ImportPackageBuilder(env *Zlisp, name string, args []Sexp) (Sexp, error) {
+	//P("starting ImportPackageBuilder")
+	n := len(args)
+	if n != 1 && n != 2 {
+		return SexpNull, WrongNargs
+	}
+
+	var path Sexp
+	var alias string
+
+	switch n {
+	case 1:
+		path = args[0]
+	case 2:
+		path = args[1]
+		//P("import debug: alias position at args[0] is '%#v'", args[0])
+		switch sy := args[0].(type) {
+		case *SexpSymbol:
+			//P("import debug: alias is symbol, ok: '%v'", sy.name)
+			alias = sy.name
+		default:
+			return SexpNull, fmt.Errorf("import error: alias was not a symbol name")
+		}
+	}
+
+	var pth string
+	switch x := path.(type) {
+	case *SexpStr:
+		pth = x.S
+	default:
+		return SexpNull, fmt.Errorf("import error: path argument must be string")
+	}
+	if !FileExists(pth) {
+		return SexpNull, fmt.Errorf("import error: path '%s' does not exist", pth)
+	}
+
+	pkg, err := SourceFileFunction(env, "source", []Sexp{path})
+	if err != nil {
+		return SexpNull, fmt.Errorf("import error: attempt to import path '%s' resulted in: '%s'", pth, err)
+	}
+	//P("pkg = '%#v'", pkg)
+
+	asPkg, isPkg := pkg.(*Stack)
+	if !isPkg || !asPkg.IsPackage {
+		return SexpNull, fmt.Errorf("import error: attempt to import path '%s' resulted value that was not a package, but rather '%T'", pth, pkg)
+	}
+
+	if n == 1 {
+		alias = asPkg.PackageName
+	}
+	//P("using alias = '%s'", alias)
+
+	// now set alias in the current env
+	err = env.LexicalBindSymbol(env.MakeSymbol(alias), asPkg)
+	if err != nil {
+		return SexpNull, err
+	}
+
+	return pkg, nil
+}