Data update

Task/CUSIP/R/cusip.r

@@ -0,0 +1,25 @@
+library(stringr)
+
+cusip_checkdigit <- function(s){
+  sum <- 0
+  chars <- str_split_1(s,"")
+  for(i in 1:8){
+    if(str_detect(chars[i],"[0-9]")) v <- as.numeric(chars[i])
+    else if(str_detect(chars[i],"[A-Z]")) v <- 9+which(LETTERS==chars[i])
+    else v <- switch(chars[i], "*"=36, "@"=37, "#"=38)
+    if(i%%2==0) v <- 2*v
+    sum <- sum+v%/%10+v%%10
+  }
+  return((10-(sum%%10))%%10)
+}
+
+cusip_isvalid <- function(s){
+  if(str_length(s)!=9){
+    stop("CUSIP must have exactly 9 characters")
+  }
+  checksum <- cusip_checkdigit(s) |> as.character()
+  ifelse(endsWith(s, checksum), "Valid CUSIP", "Invalid CUSIP")
+}
+
+test_cusips <- c("037833100","17275R102","38259P508","594918104","68389X106","68389X105")
+sapply(test_cusips, cusip_isvalid)