"The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software."
And imagine if Microsoft had been able to copyright the fast inverse square function before Carmack sat down to write Quake!
And copyright doesn't prevent someone else from implementing the same algorithm, only from copying the code. If Microsoft had been able to copyright the fast inverse square root function, Carmack could still have written his own version and even copyrighted that version himself.
Here’s an example: https://scholar.google.com/scholar_case?case=728470765881077...
It seems particularly apt to consider prior art for use in software IP if only for the similarities with the patentable invention of mechanical parts.
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Considering de novo the evidence before the district court, we hold that the district court did not err in granting summary judgment. Johannsongs failed to offer admissible evidence to rebut Ferrara's analysis, so there is no genuine dispute of material fact as to his conclusions that Söknuður and You Raise Me Up are not substantially similar and most of their similarities are attributable to prior art. Based on these conclusions, Johannsongs has failed to satisfy the extrinsic test and Defendants are entitled to judgment as a matter of law.