-- Copyright 1993-1999 by Daniel R. Grayson -- TODO: implement a copy-free accumulate and fold without reverse and drop in the interpreter -- One solution is to use iterators; see https://github.com/Macaulay2/M2/issues/1904 needs "methods.m2" accumulate = method() accumulate(Function, Thing, VisibleList) := VisibleList => accumulate(Function, Thing, Thing) := Iterator => (f, x, v) -> ( apply(v, y -> x = f(x, y))) accumulate(VisibleList,Thing,Function) := VisibleList => (v,x,f) -> reverse apply(reverse v, w -> x = f(w,x)) accumulate(Function,VisibleList) := VisibleList => (f,v) -> ( if #v === 0 then error "expected a nonempty list"; accumulate(f,v#0,drop(v,1))) accumulate(VisibleList,Function) := VisibleList => (v,f) -> ( if #v === 0 then error "expected a nonempty list"; accumulate(drop(v,-1),v#-1,f)) accumulate(Function, Thing) := Iterator => (f, v) -> ( iter := iterator v; x := next iter; if x === StopIteration then error "expected a nonempty iterator" else accumulate(f, x, iter)) fold = method() fold(Function,Thing,Thing) := foldL fold(VisibleList,Thing,Function) := (v,x,f) -> (scan(reverse v, w -> x = f(w,x)); x) fold(Function,VisibleList) := (f,v) -> ( if # v === 0 then error "expected a nonempty list"; fold(f,v#0,drop(v,1))) fold(VisibleList,Function) := (v,f) -> ( if #v === 0 then error "expected a nonempty list"; fold(drop(v,-1),v#-1,f)) fold(Function, Thing) := (f, v) -> ( iter := iterator v; x := next iter; if x === StopIteration then error "expected a nonempty iterator" else fold(f, x, iter)) demark = (s,v) -> concatenate between(s,v) -- Local Variables: -- compile-command: "make -C $M2BUILDDIR/Macaulay2/m2 " -- End:

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