Field.mask_top: def of bend-collections-laws-crypto@1.0.0.0
Import: import bend-collections-laws-crypto@1.0.0.0/src/crypto/curve25519/field.bend as Field
Lines 275-285 of bend-collections-laws-crypto@1.0.0.0/src/crypto/curve25519/field.bend: https://jend.leeeet.dev/read.txt?path=bend-collections-laws-crypto@1.0.0.0/src/crypto/curve25519/field.bend&start_line=275&end_line=285

import Base

# the last byte with its top bit cleared (RFC 7748 decodeUCoordinate)
def mask_top(xs: List<&2, U32>) -> List<&2, U32>:
  match xs:
    case Nil{}:
      Nil{}
    case Con{x, xt}:
      match xt:
        case Nil{}:
          Con{U32.and(x, 127), Nil{}}
        case Con{y, yt}:
          Con{x, mask_top(Con{y, yt})}

Uses (3):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32.and