4 5 Predef.length Predef.nonExist \v0 -> Predef.length v0 "ab" "cd" "d" "abc" "ABCD" "abcd" Predef.PFalse Predef.PTrue Predef.PFalse "no" "yes" "no" Predef.PTrue Predef.PTrue Predef.PFalse Predef.PTrue Predef.PTrue Predef.PFalse Predef.PTrue Predef.PFalse Predef.PTrue 5 user error "x" ++ Predef.nonExist ++ "y" "x" ++ Predef.BIND ++ "y" "x" ++ Predef.SOFT_BIND ++ "y" "x" ++ Predef.SOFT_SPACE ++ "y" "x" ++ Predef.CAPIT ++ "y" "x" ++ Predef.ALL_CAPIT ++ "y" "ab" \v0 -> v0 + "b" Predef.PTrue