Handle eof in file IO

1 files 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)