gsoc-bournish.diff

diff --git a/guix/build/bournish.scm b/guix/build/bournish.scm
index 928bef5..60eb899 100644
--- a/guix/build/bournish.scm
+++ b/guix/build/bournish.scm
@@ -162,6 +162,20 @@ characters."
         (else
          `((@@ (guix build bournish) wc-command-implementation) ,@args))))

+(define (bash-command-implementation commands)
+  (define-peg-pattern command-list all (and (* cmd) (not-followed-by peg-any)))
+  (define-peg-pattern parser all (or aand oor break))
+  (define-peg-pattern aand all "&&")
+  (define-peg-pattern oor all "||")
+  (define-peg-pattern pipe all (and "|" (not-followd-by (+ "|"))))
+  (define-peg-pattern break all ";")
+  (define-peg-pattern echo body "echo")
+
+  (peg:tree (match-pattern command-list commands)))
+
+(define (bash-command . args)
+  `((@@ (guix build bournish) bash-command-implementation) ,@args))
+
 (define (help-command . _)
   (display "\
 Hello, this is Bournish, a minimal Bourne-like shell in Guile!
@@ -189,7 +203,8 @@ commands such as 'ls' and 'cd'; it lacks globbing, pipes---everything.\n"))
     ("ls"     ,ls-command)
     ("which"  ,which-command)
     ("cat"    ,cat-command)
-    ("wc"     ,wc-command)))
+    ("wc"     ,wc-command)
+    ("bash"   ,bash-command)))

 (define (read-bournish port env)
   "Read a Bournish expression from PORT, and return the corresponding Scheme

Guix_GSoC_2016

My GSoC project started as a Bourne-shell compiler front-end for guile. To this end
I spent some time learning guile and wrote an implementation of 'wc' for
guix/build/bournish.scm. From there one of my mentors Ludovic suggested that I take
a look at PEG parsing, using the development branch of guile, to turn my attention
from reimplementing the programs in coreutils to the actual parsing of commands,
which would allow us to chain together commands, much as is done from the command
line or while compiling programs. Unfortunately this proved to be a larger project
than I had time left for during GSoC, so I have not yet made a lot of progress on
that front.

To this end I do plan on continuing my work after the end of GSoC, I want to get
the parsing down and I want to see how far I can push this and how much it can be
integrated into the project.