Capturing output of scheme evaluations

2 files changed, 9 insertions, 4 deletions

diff --git a/elisp/geiser-eval.el b/elisp/geiser-eval.el
index 5369a1f..68ef1ca 100644
--- a/elisp/geiser-eval.el
+++ b/elisp/geiser-eval.el
@@ -108,6 +108,7 @@
 (defsubst geiser-eval--retort-p (ret)
   (and (listp ret) (or (assoc 'error ret) (assoc 'result ret))))
 (defsubst geiser-eval--retort-result (ret) (cdr (assoc 'result ret)))
+(defsubst geiser-eval--retort-output (ret) (cdr (assoc 'output ret)))
 (defsubst geiser-eval--retort-error (ret) (cdr (assoc 'error ret)))
 
 (defsubst geiser-eval--error-key (err) (cdr (assoc 'key err)))
diff --git a/scheme/geiser/eval.scm b/scheme/geiser/eval.scm
index 81b2647..450221a 100644
--- a/scheme/geiser/eval.scm
+++ b/scheme/geiser/eval.scm
@@ -31,16 +31,20 @@
 (define (eval-in form module-name)
   "Evals FORM in the module designated by MODULE-NAME.
 If MODULE-NAME is #f or resolution fails, the current module is used instead.
-The result is a list of the form ((RESULT . <form-value>))
+The result is a list of the form ((RESULT . <form-value>) (OUTPUT . <string>))
 if no evaluation error happens, or ((ERROR (KEY . <error-key>) <error-arg>...))
 in case of errors. Each error arg is a cons (NAME . VALUE), where NAME includes
 SUBR, MSG and REST."
   (let ((module (or (and module-name (resolve-module module-name))
                     (current-module))))
     (catch #t
-      (lambda () (list (cons 'result (eval form module))))
-      (lambda (key . args)
-        (list (cons 'error (apply parse-error (cons key args))))))))
+           (lambda ()
+             (let* ((result #f)
+                    (output (with-output-to-string
+                              (lambda () (set! result (eval form module))))))
+               (list (cons 'result result) (cons 'output output))))
+           (lambda (key . args)
+             (list (cons 'error (apply parse-error (cons key args))))))))
 
 (define (parse-error key . args)
   (let* ((len (length args))