From 28d0c259edbbb9d0f0ac91edd3e04d3419c673a3 Mon Sep 17 00:00:00 2001
From: Jan Nieuwenhuizen <janneke@gnu.org>
Date: Thu, 4 Jan 2018 18:35:26 +0100
Subject: [PATCH] mes: with-input-from-string: peek fix.

* module/mes/guile.mes (with-input-from-string): Return actual tell.
* tests/guile.test ("with-input-from-string peek"): Test it.
---
 module/mes/guile.mes | 5 +++--
 tests/guile.test     | 5 +++++
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/module/mes/guile.mes b/module/mes/guile.mes
index 4122c6d8..bd2f3bb4 100644
--- a/module/mes/guile.mes
+++ b/module/mes/guile.mes
@@ -71,8 +71,9 @@
   (let ((tell 0)
         (end (string-length string)))
     (set! peek-char
-          (lambda () (if (= tell end) (integer->char -1)
-                         (string-ref string (- tell 1)))))
+          (lambda ()
+            (if (= tell end) (integer->char -1)
+                (string-ref string tell))))
     (set! read-char
           (lambda () (if (= tell end) (integer->char -1)
                          (begin
diff --git a/tests/guile.test b/tests/guile.test
index 4a3366be..0af3b35e 100755
--- a/tests/guile.test
+++ b/tests/guile.test
@@ -112,4 +112,9 @@ exit $?
     (push-input sp)
     (and (pop-input) (not (pop-input)))))
 
+(pass-if-equal "with-input-from-string peek"
+               #\X
+               (with-input-from-string "X"
+                 (lambda () (peek-char))))
+
 (result 'report)