def prod_fold

bend-collections-laws-math@1.0.0.0 · proofs/math/typed/float.bend:89

import Base
import bend-collections-laws-math@1.0.0.0/spec/math/generic.bend as SG
import bend-collections-laws-math@1.0.0.0/src/math/generic.bend as G
import bend-collections-laws-math@1.0.0.0/src/math/num.bend as N

89def prod_fold(~T: Data, ~op: N.Op<T> -> T, ~test: N.Test<T> -> Bool, ~mo: NoMulOver(~T, ~test), xs: List<&2, T>, +acc: T) -> {G.prod_go(~T, ~op, ~test, xs, Some{acc}) == Some{SG.fold_mul(~T, ~op, xs, acc)} : Maybe<&2, T>}:
90  match xs:
91    case Nil{}:
92      {==}
93    case Con{+x, t}:
94      %Equal.sym(Bool, test(N.MulOver{acc, x}), False{}, mo(acc, x)) : {G.prod_go(~T, ~op, ~test, t, G.fits(T, _, op(N.Mul{acc, x}))) == Some{SG.fold_mul(~T, ~op, t, op(N.Mul{acc, x}))} : Maybe<&2, T>}
95      prod_fold(~T, ~op, ~test, ~mo, t, op(N.Mul{acc, x}))