As others comments have pointed out - you may want to brush up on those definitions. Correct semantics are crucial. They're a form of compression with no/low error correction.

Any claims of injective or surjective properties (and by extension bijection) are moot without the domain and co-domain being specified.

To map math ↦ dev semantics: functions need to be pure, deterministic and declared with strong types. The properties of square root in particular will vary wildly based on what those types are.