Update tripleword.jl

Author: JeffreySarnoff

src/doubletriple/tripleword.jl

@@ -4,6 +4,13 @@
  Nicolas Fabiano, Jean-Michel Muller, Joris Picot
 =#
 
+function vecsum3(x0::T, x1::T, x2::T) where {T}
+    s1, e2 = two_sum(x1, x2)
+    s0, e1 = two_sum(x0, s1)
+    return s0,e1,e2
+end
+
+
 function vecsum(x0::T,x1::T,x2::T) where {T}
    x0 === 0.0 && return (two_sum(x1, x2)..., 0.0)
    s1, e2 = two_sum(x1, x2)