# Source Location and Ancillary Source File Support

The :std/source library provides common macros to access the source location of code being read, interpreted or compiled, and to ancillary files next to the source files proper, that may provide data used at either runtime or compile-time.

(import :std/source)

# this-source-location

(this-source-location [context])

Expands to the location of the supplied context source form, or to the this-source-location invocation itself if left implicit.

The location is a vector #(file pos) in standard Gambit fashion:

• file is either a string with the file name from which the source was read, or if it was not read from a file, something such as the list (stdin).
• pos is a positive fixnum of the form (+ (* column 65536) line) where both the line and column start at zero (whereas most other software including e.g. Emacs count line from one, and Emacs counts column from 0), if line and column are both under 65536, or else a negative integer, the opposite of the file or port position.

> (quotient (vector-ref (this-source-location) 1) 65536)
23

# this-source-file

(this-source-file [context])

Expands to the file path of the supplied context source form, or to the this-source-file invocation itself if left implicit.

#!/usr/bin/env gxi
(import :std/source)
(def $0 (this-source-file))
;;; Now you can play with this source file at runtime.

# this-source-directory

(this-source-directory [context])

Expands to the file directory path of the supplied context source form, or to the this-source-directory invocation itself if left implicit, so you can play with it at runtime.

#!/usr/bin/env gxi
(import :std/source :std/misc/path :std/misc/ports)
(def $this-dir (this-source-directory))
(def data (read-all-as-lines (subpath $this-dir "data.txt")))

# this-source-path

(this-source-path [context] relpath)

Given the source-file the supplied context source form was read from, return the expanded path relative to the path-directory of that source-file under the relpath relative path.

#!/usr/bin/env gxi
(import :std/source :std/misc/ports)
(def data (read-all-as-lines (this-source-path "data.txt")))

# this-source-content

(this-source-content [context] relpath)

Given the source-file the supplied context source form was read from, return as a u8vector the content of a file relative to the path-directory of that source-file, burnt into your object file at compile time, so the ancillary file doesn't have to exist anymore at runtime.

You may find creative uses of syntax-call and and syntax-eval to further manipulate data at compile-time.