using cross2 for Iteration

colors <- c("red", "green", "yellow")
vehicles <- c("bicycle", "car", "submarine", "airplane")

crossing(colors,vehicles)

## # A tibble: 12 x 2
##    colors vehicles 
##    <chr>  <chr>    
##  1 green  airplane 
##  2 green  bicycle  
##  3 green  car      
##  4 green  submarine
##  5 red    airplane 
##  6 red    bicycle  
##  7 red    car      
##  8 red    submarine
##  9 yellow airplane 
## 10 yellow bicycle  
## 11 yellow car      
## 12 yellow submarine

colored_vehicles <- purrr::cross2(colors, vehicles) %>% 
  purrr::map_chr(~paste(.[[1]], .[[2]]))

colored_vehicles 

##  [1] "red bicycle"      "green bicycle"    "yellow bicycle"   "red car"         
##  [5] "green car"        "yellow car"       "red submarine"    "green submarine" 
##  [9] "yellow submarine" "red airplane"     "green airplane"   "yellow airplane"

a <- 11:15
b <- 1:3

output <- purrr::cross2(a, b) %>% 
  purrr::map_dbl(~( .[[1]] * .[[2]] ))

output

##  [1] 11 12 13 14 15 22 24 26 28 30 33 36 39 42 45