520: add function identity and use it in deep-equal #525
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Accepted at meeting 036 |
This was referenced Jun 9, 2023
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michaelhkay
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I believe this PR resolves issues
issue #520 - function identity
issue #333 - equality of function items
issue #381 - deep-equal comparison without errors
The PR introduces a concept of function identity in the data model, and for all expressions that create functions, explains what the identity of the returned function is.
The concept of function identity is used initially in two places: in fn:deep-equal(), when the operands include function items; and in the F+O prose defining the concept of determinism, which in turn is relied on by the definition of memo functions in XSLT.
I had hoped to go further and address issue #119, generalising what kinds of values are allowed as keys in maps, but as explained in a comment on that issue, I hit obstacles.