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juvix/tests/positive/Termination/Fib.juvix
Jan Mas Rovira 8daca2ba0a
New fixity/iterator syntax (#2332)
- Closes #2330
- Closes #2329 

This pr implements the syntax changes described in #2330. It drops
support for the old yaml-based syntax.
Some valid examples:
```
syntax iterator for {init := 1; range := 1};

syntax fixity cons := binary {assoc := right};
syntax fixity cmp := binary;
syntax fixity cmp := binary {}; -- debatable whether we want to accept empty {} or not. I think we should
```
# Future work
This pr creates an asymmetry between iterators and operators
definitions. Iterators definition do not require a constructor. We could
add it to make it homogeneous, but it looks a bit redundant:
```
syntax iterator for := mkIterator {init := 1; range := 1};
```

We could consider merging iterator and fixity declarations with this
alternative syntax.
```
syntax XXX for := iterator {init := 1; range := 1};

syntax XXX cons := binary {assoc := right};
```
where `XXX` is a common keyword. Suggestion by @lukaszcz XXX = declare

---------

Co-authored-by: Łukasz Czajka <62751+lukaszcz@users.noreply.github.com>
Co-authored-by: Lukasz Czajka <lukasz@heliax.dev>
2023-09-14 10:57:38 +02:00

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module Fib;
syntax fixity add := binary {assoc := left};
type Nat :=
| zero : Nat
| suc : Nat → Nat;
syntax operator + add;
+ : Nat → Nat → Nat
| zero b := b
| (suc a) b := suc (a + b);
fib : Nat -> Nat
| zero := zero
| (suc zero) := suc zero
| (suc (suc n)) := fib (suc n) + fib n;