X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=matita%2Fmatita%2Fcontribs%2Flambdadelta%2Fbasic_2%2Frt_transition%2Fhls.ml;h=d796a4a66c8293d076d36a75083540aeb3e810fc;hb=b5ded5b0c305b30349339b24760820154f7de390;hp=01f59045d18adb38f6dd3652f8002996ac2f282d;hpb=d64caa33426da23e1ab75eca50f227c40e95a24b;p=helm.git

diff --git a/matita/matita/contribs/lambdadelta/basic_2/rt_transition/hls.ml b/matita/matita/contribs/lambdadelta/basic_2/rt_transition/hls.ml
index 01f59045d..d796a4a66 100644
--- a/matita/matita/contribs/lambdadelta/basic_2/rt_transition/hls.ml
+++ b/matita/matita/contribs/lambdadelta/basic_2/rt_transition/hls.ml
@@ -1,4 +1,6 @@
-let cols = int_of_string (Sys.getenv "COLUMNS")
+let cols =
+   try int_of_string (Sys.getenv "COLUMNS")
+   with Not_found -> failwith "environment variable COLUMNS not visible"
 
 let hl = ref []
 
@@ -52,3 +54,4 @@ let main =
    Array.fast_sort compare files;
    let c = Array.fold_left (write l) 0 files in
    if 0 < c && c < cols then print_newline ();
+