ocaml

Not sure why I'm getting unbound value when used with List.iter


I'm writing test code for my OCaml project and when using the below code, it works fine.

open Printf
open Ip2location

(* query IP2Location BIN datababase *)
let meta = Database.open_db "./IP2LOCATION-LITE-DB1.IPV6.BIN";;

let ip = "2a02:3037:0400:6fa2:459c:84b6:967d:69e0";;
let res = Database.query meta ip;;

printf "country_short: %s\n" res.country_short;;
printf "country_long: %s\n" res.country_long;;
printf "region: %s\n" res.region;;
printf "city: %s\n" res.city;;
printf "isp: %s\n" res.isp;;
printf "latitude: %f\n" res.latitude;;
printf "longitude: %f\n" res.longitude;;
printf "domain: %s\n" res.domain;;
printf "zip_code: %s\n" res.zip_code;;
printf "time_zone: %s\n" res.time_zone;;
printf "net_speed: %s\n" res.net_speed;;
printf "idd_code: %s\n" res.idd_code;;
printf "area_code: %s\n" res.area_code;;
printf "weather_station_code: %s\n" res.weather_station_code;;
printf "weather_station_name: %s\n" res.weather_station_name;;
printf "mcc: %s\n" res.mcc;;
printf "mnc: %s\n" res.mnc;;
printf "mobile_brand: %s\n" res.mobile_brand;;
printf "elevation: %f\n" res.elevation;;
printf "usage_type: %s\n" res.usage_type;;
printf "address_type: %s\n" res.address_type;;
printf "category: %s\n" res.category;;
printf "district: %s\n" res.district;;
printf "asn: %s\n" res.asn;;
printf "as: %s\n" res.asys;;

Database.close_db meta;;

Then, I modified the code to query a list of IP addresses like below:

open Printf
open Ip2location

(* query IP2Location BIN datababase *)
let meta = Database.open_db "./IP2LOCATION-LITE-DB1.IPV6.BIN";;

let mylist = ["0.0.0.0"; "8.3.34.0"; "8.8.8.8"; "3.91.171.8"; "37.252.228.50"; "64.94.62.0"; "197.85.191.64"; "255.255.255.254"; "255.255.255.255"; "179.125.12.0"; "::"; "2001::"; "2001:0:4136:e378:8000:63bf:f7f7:f7f7"; "2001:0000:4136:e378:8000:63bf:f7fc:ddff"; "2002::"; "2002:808:808::"; "2002:0803:2200::0803:2200"; "2600:1F18:45B0:5B00:0000:0000:0000:0000"; "::FFFF:FFFF"; "::FFFF:3.91.171.8"; "::FFFF:8.3.34.0"; "::FFFF:64.94.62.0"; "::FFFF:C555:BF40"; "ffff:ffff:ffff:ffff:FFFF:FFFF:FFFF:FFFE"; "FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF"; "0:0:0:0:0:ffff:b37d:0c00"; "0.0.0.256"; "0.0.0"; "1"; "A"];;

let getloc ip =
    let res = Database.query meta ip in
    printf "country_short: %s\n" res.country_short;;
    printf "country_long: %s\n" res.country_long;;
    printf "region: %s\n" res.region;;
    printf "city: %s\n" res.city;;
    printf "isp: %s\n" res.isp;;
    printf "latitude: %f\n" res.latitude;;
    printf "longitude: %f\n" res.longitude;;
    printf "domain: %s\n" res.domain;;
    printf "zip_code: %s\n" res.zip_code;;
    printf "time_zone: %s\n" res.time_zone;;
    printf "net_speed: %s\n" res.net_speed;;
    printf "idd_code: %s\n" res.idd_code;;
    printf "area_code: %s\n" res.area_code;;
    printf "weather_station_code: %s\n" res.weather_station_code;;
    printf "weather_station_name: %s\n" res.weather_station_name;;
    printf "mcc: %s\n" res.mcc;;
    printf "mnc: %s\n" res.mnc;;
    printf "mobile_brand: %s\n" res.mobile_brand;;
    printf "elevation: %f\n" res.elevation;;
    printf "usage_type: %s\n" res.usage_type;;
    printf "address_type: %s\n" res.address_type;;
    printf "category: %s\n" res.category;;
    printf "district: %s\n" res.district;;
    printf "asn: %s\n" res.asn;;
    printf "as: %s\n" res.asys

List.iter getloc mylist;;

Database.close_db meta;;

When I ran dune test, I get the below:

File "test/ip2locationtest.ml", line 12, characters 29-32:
12 |    printf "country_long: %s\n" res.country_long;;
                                    ^^^
Error: Unbound value res
Hint: Did you mean ref?

I am a newbie in OCaml so I am not sure what I'm missing. Would appreciate any pointers on what I'm doing wrong.


Solution

  • The double semicolon ;; is used to mark the end of an expression when talking to the interpreter. Hence your let res = ... ends at the first double semicolon. After that res is no longer defined.

    You should't really use double semicolons in code. It's just a way of talking to the interpreter (the OCaml REPL, aka "top-level"). If you change your double semicolons to single semicolons things will work better.