support expression-by-expression compilation

* module/language/ghil.scm (unparse-ghil): Fix unparsing of quasiquoted
  expressions.

* module/language/ghil/spec.scm (join): Define a joiner for GHIL.

* module/language/scheme/compile-ghil.scm (cenv-ghil-env): Expand the
  definition of a CENV so it can have an actual ghil-env, if available.
  (compile-ghil): Return the actual ghil env in the cenv.

* module/system/base/compile.scm (compile-file): Rewrite. `output-file'
  is now a keyword argument, along with the new kwargs `env' and `from'.
  We now allow exceptions to propagate up, and instead of printing the
  output file to the console, we return a string corresponding to its
  location.
  (compile-and-load): Use read-and-compile.
  (compile-fold): Thread around the cenv as well. Return all three
  values.
  (find-language-joint, read-and-compile): New exciting helpers. The idea
  is that compiling a file should be semantically equivalent to compiling
  each expression in it, one by one. Compilation can have side effects,
  e.g. affecting the current language or the current reader. So what we
  do is find a point in the compilation path at which different
  expressions of a given language can be joined into one. Expressions
  from the source language are compiled to the joint language, then
  joined and compiled to the target.
  (compile): Just return the first value from compile-fold.

* module/system/base/language.scm (language-joiner): New optional field.

* scripts/compile: Rework for changes to compile-file.

scripts/compile

@@ -28,9 +28,7 @@ exec ${GUILE-guile} -e '(@ (scripts compile) compile)' -s $0 "$@"
 
 ;; Usage: compile [ARGS]
 ;;
-;; PROGRAM does something.
-;;
-;; TODO: Write it!
+;; A command-line interface to the Guile compiler.
 
 ;;; Code:
 
@@ -67,15 +65,16 @@ exec ${GUILE-guile} -e '(@ (scripts compile) compile)' -s $0 "$@"
 	(option '(#\O "optimize") #f #f
 		(lambda (opt name arg result)
 		  (alist-cons 'optimize? #t result)))
-	(option '(#\e "expand-only") #f #f
+	(option '(#\f "from") #t #f
 		(lambda (opt name arg result)
-		  (alist-cons 'expand-only? #t result)))
-	(option '(#\t "translate-only") #f #f
+                  (if (assoc-ref result 'from)
+                      (fail "`--from' option cannot be specified more than once")
+                      (alist-cons 'from (string->symbol arg) result))))
+	(option '(#\t "to") #t #f
 		(lambda (opt name arg result)
-		  (alist-cons 'translate-only? #t result)))
-	(option '(#\c "compile-only") #f #f
-		(lambda (opt name arg result)
-		  (alist-cons 'compile-only? #t result)))))
+                  (if (assoc-ref result 'to)
+                      (fail "`--to' option cannot be specified more than once")
+                      (alist-cons 'to (string->symbol arg) result))))))
 
 (define (parse-args args)
   "Parse argument list @var{args} and return an alist with all the relevant
@@ -97,46 +96,44 @@ options."
 (define (compile args)
   (let* ((options         (parse-args (cdr args)))
          (help?           (assoc-ref options 'help?))
-         (optimize?       (assoc-ref options 'optimize?))
-         (expand-only?    (assoc-ref options 'expand-only?))
-         (translate-only? (assoc-ref options 'translate-only?))
-         (compile-only?   (assoc-ref options 'compile-only?))
+         (compile-opts    (if (assoc-ref options 'optimize?) '(#:O) '()))
+         (from            (or (assoc-ref options 'from) 'scheme))
+         (to              (or (assoc-ref options 'to) 'objcode))
 	 (input-files     (assoc-ref options 'input-files))
 	 (output-file     (assoc-ref options 'output-file))
 	 (load-path       (assoc-ref options 'load-path)))
     (if (or help? (null? input-files))
         (begin
           (format #t "Usage: compile [OPTION] FILE...
-Compile each Guile Scheme source file FILE into a Guile object.
+Compile each Guile source file FILE into a Guile object.
 
   -h, --help           print this help message
 
   -L, --load-path=DIR  add DIR to the front of the module load path
   -o, --output=OFILE   write output to OFILE
 
-  -O, --optimize       turn on optimizations
-  -e, --expand-only    only go through the code expansion stage
-  -t, --translate-only stop after the translation to GHIL
-  -c, --compile-only   stop after the compilation to GLIL
+  -f, --from=LANG      specify a source language other than `scheme'
+  -t, --to=LANG        specify a target language other than `objcode'
 
 Report bugs to <guile-user@gnu.org>.~%")
           (exit 0)))
 
     (set! %load-path (append load-path %load-path))
 
-    (let ((compile-opts (append (if optimize? '(#:O) '())
-                                (if expand-only? '(#:e) '())
-                                (if translate-only? '(#:t) '())
-                                (if compile-only? '(#:c) '()))))
-      (if output-file
-	  (if (and (not (null? input-files))
-		   (null? (cdr input-files)))
-	      (compile-file (car input-files) output-file)
-	      (fail "`-o' option can only be specified "
-		    "when compiling a single file"))
-	  (for-each (lambda (file)
-		      (apply compile-file file compile-opts))
-		    input-files)))))
+    (if (and output-file
+             (or (null? input-files)
+                 (not (null? (cdr input-files)))))
+        (fail "`-o' option can only be specified "
+              "when compiling a single file"))
+
+    (for-each (lambda (file)
+                (format #t "wrote `~A'\n"
+                        (compile-file file
+                                      #:output-file output-file
+                                      #:from from
+                                      #:to to
+                                      #:opts compile-opts)))
+              input-files)))
 
 ;;; Local Variables:
 ;;; coding: latin-1