def set_top

bend-collections-laws-crypto@1.0.0.0 · src/crypto/ed25519/point.bend:113

import Base

113# the last byte with bit 7 set to b (the canonical y has it clear)
114def set_top(xs: List<&2, U32>, +b: U32) -> List<&2, U32>:
115  match xs:
116    case Nil{}:
117      Nil{}
118    case Con{x, xt}:
119      match xt:
120        case Nil{}:
121          Con{U32.or(x, U32.shln(b, 7n)), Nil{}}
122        case Con{y, yt}:
123          Con{x, set_top(Con{y, yt}, b)}