expressions working

Signed-off-by: Casey Lee <cplee@nektos.com>

vendor/github.com/robertkrimen/otto/file/README.markdown

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+# file
+--
+    import "github.com/robertkrimen/otto/file"
+
+Package file encapsulates the file abstractions used by the ast & parser.
+
+## Usage
+
+#### type File
+
+```go
+type File struct {
+}
+```
+
+
+#### func  NewFile
+
+```go
+func NewFile(filename, src string, base int) *File
+```
+
+#### func (*File) Base
+
+```go
+func (fl *File) Base() int
+```
+
+#### func (*File) Name
+
+```go
+func (fl *File) Name() string
+```
+
+#### func (*File) Source
+
+```go
+func (fl *File) Source() string
+```
+
+#### type FileSet
+
+```go
+type FileSet struct {
+}
+```
+
+A FileSet represents a set of source files.
+
+#### func (*FileSet) AddFile
+
+```go
+func (self *FileSet) AddFile(filename, src string) int
+```
+AddFile adds a new file with the given filename and src.
+
+This an internal method, but exported for cross-package use.
+
+#### func (*FileSet) File
+
+```go
+func (self *FileSet) File(idx Idx) *File
+```
+
+#### func (*FileSet) Position
+
+```go
+func (self *FileSet) Position(idx Idx) *Position
+```
+Position converts an Idx in the FileSet into a Position.
+
+#### type Idx
+
+```go
+type Idx int
+```
+
+Idx is a compact encoding of a source position within a file set. It can be
+converted into a Position for a more convenient, but much larger,
+representation.
+
+#### type Position
+
+```go
+type Position struct {
+	Filename string // The filename where the error occurred, if any
+	Offset   int    // The src offset
+	Line     int    // The line number, starting at 1
+	Column   int    // The column number, starting at 1 (The character count)
+
+}
+```
+
+Position describes an arbitrary source position including the filename, line,
+and column location.
+
+#### func (*Position) String
+
+```go
+func (self *Position) String() string
+```
+String returns a string in one of several forms:
+
+    file:line:column    A valid position with filename
+    line:column         A valid position without filename
+    file                An invalid position with filename
+    -                   An invalid position without filename
+
+--
+**godocdown** http://github.com/robertkrimen/godocdown

vendor/github.com/robertkrimen/otto/file/file.go

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+// Package file encapsulates the file abstractions used by the ast & parser.
+//
+package file
+
+import (
+	"fmt"
+	"strings"
+
+	"gopkg.in/sourcemap.v1"
+)
+
+// Idx is a compact encoding of a source position within a file set.
+// It can be converted into a Position for a more convenient, but much
+// larger, representation.
+type Idx int
+
+// Position describes an arbitrary source position
+// including the filename, line, and column location.
+type Position struct {
+	Filename string // The filename where the error occurred, if any
+	Offset   int    // The src offset
+	Line     int    // The line number, starting at 1
+	Column   int    // The column number, starting at 1 (The character count)
+
+}
+
+// A Position is valid if the line number is > 0.
+
+func (self *Position) isValid() bool {
+	return self.Line > 0
+}
+
+// String returns a string in one of several forms:
+//
+//	file:line:column    A valid position with filename
+//	line:column         A valid position without filename
+//	file                An invalid position with filename
+//	-                   An invalid position without filename
+//
+func (self *Position) String() string {
+	str := self.Filename
+	if self.isValid() {
+		if str != "" {
+			str += ":"
+		}
+		str += fmt.Sprintf("%d:%d", self.Line, self.Column)
+	}
+	if str == "" {
+		str = "-"
+	}
+	return str
+}
+
+// FileSet
+
+// A FileSet represents a set of source files.
+type FileSet struct {
+	files []*File
+	last  *File
+}
+
+// AddFile adds a new file with the given filename and src.
+//
+// This an internal method, but exported for cross-package use.
+func (self *FileSet) AddFile(filename, src string) int {
+	base := self.nextBase()
+	file := &File{
+		name: filename,
+		src:  src,
+		base: base,
+	}
+	self.files = append(self.files, file)
+	self.last = file
+	return base
+}
+
+func (self *FileSet) nextBase() int {
+	if self.last == nil {
+		return 1
+	}
+	return self.last.base + len(self.last.src) + 1
+}
+
+func (self *FileSet) File(idx Idx) *File {
+	for _, file := range self.files {
+		if idx <= Idx(file.base+len(file.src)) {
+			return file
+		}
+	}
+	return nil
+}
+
+// Position converts an Idx in the FileSet into a Position.
+func (self *FileSet) Position(idx Idx) *Position {
+	for _, file := range self.files {
+		if idx <= Idx(file.base+len(file.src)) {
+			return file.Position(idx - Idx(file.base))
+		}
+	}
+
+	return nil
+}
+
+type File struct {
+	name string
+	src  string
+	base int // This will always be 1 or greater
+	sm   *sourcemap.Consumer
+}
+
+func NewFile(filename, src string, base int) *File {
+	return &File{
+		name: filename,
+		src:  src,
+		base: base,
+	}
+}
+
+func (fl *File) WithSourceMap(sm *sourcemap.Consumer) *File {
+	fl.sm = sm
+	return fl
+}
+
+func (fl *File) Name() string {
+	return fl.name
+}
+
+func (fl *File) Source() string {
+	return fl.src
+}
+
+func (fl *File) Base() int {
+	return fl.base
+}
+
+func (fl *File) Position(idx Idx) *Position {
+	position := &Position{}
+
+	offset := int(idx) - fl.base
+
+	if offset >= len(fl.src) || offset < 0 {
+		return nil
+	}
+
+	src := fl.src[:offset]
+
+	position.Filename = fl.name
+	position.Offset = offset
+	position.Line = strings.Count(src, "\n") + 1
+
+	if index := strings.LastIndex(src, "\n"); index >= 0 {
+		position.Column = offset - index
+	} else {
+		position.Column = len(src) + 1
+	}
+
+	if fl.sm != nil {
+		if f, _, l, c, ok := fl.sm.Source(position.Line, position.Column); ok {
+			position.Filename, position.Line, position.Column = f, l, c
+		}
+	}
+
+	return position
+}