# \DeclareMathOperator vs. \operatorname*

To define my own math operators, I usually use amsmath's \DeclareMathOperator. However, with \DeclareMathOperator{\Res}{Res} does not give me the desired "limits" under the operator even in displayed math.

Searching this site, I found \operatorname* (and \operatornamewithlimits) which implements the desired behavior.

$$\operatorname*{Res}_{x = y} \frac{1}{x - y} = 1.$$


gives

However, I'm still unsure if this can or should somehow be combined with \DeclareMathOperator and generally when to choose \operatorname* over \DeclareMathOperator (besides this particular case).

• You have \DeclareMathOperator*. – Bernard Aug 30 '17 at 15:13
• @Bernard Ah, I might have guessed... :) – Casimir Aug 30 '17 at 15:16
• Or have read the amsmath documentation… ;o) – Bernard Aug 30 '17 at 15:27