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docs: add explanation to sort primop

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Johannes Kirschbauer 2025-11-13 10:47:26 +07:00
parent f2253a00bc
commit af6326dfa4
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20
src/libexpr/primops.cc
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@ -4014,6 +4014,8 @@ static RegisterPrimOp primop_sort({
1. Transitivity
If a is less than b and b is less than c, then it follows that a is less than c.
```nix
comparator a b && comparator b c -> comparator a c
```
@ -4026,9 +4028,23 @@ static RegisterPrimOp primop_sort({
1. Transitivity of equivalence
First, two values a and b are considered equivalent with respect to the comparator if:
```
!comparator a b && !comparator b a
```
In other words, neither is considered "less than" the other.
Transitivity of equivalence means:
If a is equivalent to b, and b is equivalent to c, then a must also be equivalent to c.
```nix
let equiv = a: b: (!comparator a b && !comparator b a); in
equiv a b && equiv b c -> equiv a c
let
equiv = x: y: (!comparator x y && !comparator y x);
in
equiv a b && equiv b c -> equiv a c
```
If the *comparator* violates any of these properties, then `builtins.sort`