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The typical operation applied to sets of functions is composition, so idempotency of a function f is the condition that f(f(x)) = f(x) for all x in the domain o
by laneb 8y ago
The typical operation applied to sets of functions is composition, so idempotency of a function f is the condition that f(f(x)) = f(x) for all x in the domain of f. I don't think that applies meaningfully to GET.
- jholman 8y agoIt does apply to HTTP idempotency. `x` is the state of the server. `f` is the change to the state of the server that ensues when one makes such-and-such an HTTP call. So taking PUT as an example, `x` is the state before the PUT, `f(x)` is the state after one PUT, and `f(f(x))` is the state after that single PUT is sent twice. Of course in a RFC7231-compliant server, `f(x) = f(f(x))`. Taking GET (or any other nullipotent method) as an example, we also see that in a RFC7231-compliant server, `x = f(x) = f(f(x))`.
- laneb 8y agoAh yeah that makes sense.
- CapacitorSet 8y agoTechnically speaking, idempotency as defined by RFC7231 only requires f(x) = f(f(x)).
- jholman 8y agoYes, and nullipotency requires x = f(x) = f(f(x)), and four of the methods defined in RFC7231 are expected to be nullipotent, otherwise known as "safe". The point of mentioning that is to highlight the relationship between idempotence and nullipotence.