source("fred.R")

 sum.fred <- fred(1:10, 1:5, 1:3)
 sum.fred

 sum <- 0
 for (i in 1:10) {
     for (j in 1:5) {
         for (k in 1:3) {
             sum <- sum + i * j * k
         }
     }
 }
 all.equal(sum, sum.fred)

 fred(1:10)

 sum.fred <- fred(1:10, 1:5, 1:3, func = sin)
 sum.fred

 sum <- 0
 for (i in 1:10) {
     for (j in 1:5) {
         for (k in 1:3) {
             sum <- sum + sin(i) * sin(j) * sin(k)
         }
     }
 }
 all.equal(sum, sum.fred)

 ##### note: the following should crash
 fred(func = sin)