Operators cannot be mixed in the order given <= :

[ovidiugabriel]

Trying to run the example on the first page with DrRacket, version 7.7

#lang planet breuleux/liso

fib[n] =
   @if n <= 1:
      n
      fib[n - 1] + fib[n - 2]

fib[30]

I get the following error.

Welcome to DrRacket, version 7.7 [3m].
Language: planet breuleux/liso, with debugging; memory limit: 128 MB.
Operators cannot be mixed in the order given <= :

Interactions disabled.

[ovidiugabriel]

When running fact.liso

Operators cannot be mixed in the order given ! :

And so on.

[breuleux]

Yeah, I don't know, it's been too long 😬

You can try putting parentheses around n <= 1, I suppose.