From aa160950ef426bc959ddce12bd45d2af0cf8dc72 Mon Sep 17 00:00:00 2001
From: Tom Smeding <tom.smeding@gmail.com>
Date: Thu, 14 Nov 2019 17:57:42 +0100
Subject: Handle eof in file IO

---
 VM.hs | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/VM.hs b/VM.hs
index ae9dc6f..7baea0d 100644
--- a/VM.hs
+++ b/VM.hs
@@ -129,8 +129,11 @@ vmRunBuiltin state "sys-close-file" [RVNum fid] = do
     hClose (sHandles state ! fid)
     return (RVList [], state { sHandles = Map.delete fid (sHandles state) })
 vmRunBuiltin state "sys-get-char" [RVNum fid] = do
-    ch <- hGetChar (sHandles state ! fid)
-    return (RVString [ch], state)
+    let h = sHandles state ! fid
+    eof <- hIsEOF h
+    if eof
+        then return (RVList [], state)
+        else hGetChar h >>= \ch -> return (RVString [ch], state)
 vmRunBuiltin state "sys-put-string" [RVNum fid, RVString str] = do
     hPutStr (sHandles state ! fid) str
     return (RVList [], state)
-- 
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