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-rw-r--r-- | lib/js/urweb.js | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/lib/js/urweb.js b/lib/js/urweb.js index 1c296fe1..749e5056 100644 --- a/lib/js/urweb.js +++ b/lib/js/urweb.js @@ -2493,6 +2493,8 @@ function id(x) { return x; } function sub(s, i) { var ch = undefined; iterateString(s, function(c, idx) { if (idx == i) { ch = c; return false; }}); + if (ch == undefined) + er("String index " + i + " out of bounds") return ch; } function suf(s, i) { |