This paper introduces to the finite-state calculus a family of directed replace operators. In contrast to the simple replace expression, UPPER - LOWER,defined in K a r t t u n e n (1995), the new directed version, UPPER ©- LOWER, yields an unambiguous transducer if the lower language consists of a single string. It transduces the input string from left to right, making only the longest possible replacement at each point. A new type of replacement expression, UPPER @- PREFIX . . . SUFFIX, yields a transducer that inserts text around strings that are instances of UPPER. .
