def first_of

bendtorch-core@0.1.0.0 · src/autograd/tensor_vjp_LAWS.bend:77

import Base
import bendtorch-core@0.1.0.0/src/autograd/tensor_backward.bend as Backward

77# The two contributions of a VJP, when it sends exactly two.
78def first_of(pass: Backward.Pass) -> Maybe<&1, Backward.Contribution>:
79  Backward.Pass{saved, g, contributions} = pass
80  match contributions:
81    case Fail{error}:
82      None{}
83    case Done{Nil{}}:
84      None{}
85    case Done{Con{first, Nil{}}}:
86      None{}
87    case Done{Con{first, Con{second, Nil{}}}}:
88      Some{first}
89    case Done{Con{first, Con{second, Con{other, rest}}}}:
90      None{}