Problem with stored procedure

Hello,

In this example, I use 2 tables :
create table types (
typnum integer primary key,
catcode varchar(2),
typlib varchar(35));

create table uv (
uvnum varchar(5) primary key,
typnum integer,
uvlib varchar(50));

alter table uv
   add constraint fk_uv_type foreign key (typnum)
      references types (typnum)
      on delete restrict on update restrict;

I also use stored procedures :

create function numtype(varchar) returns integer as '
declare
   codetype alias for $1;
   coderet integer;
begin
   select into coderet typnum from types
       where typcode = codetype and catcode = ''UV'';
   return coderet;
end;
' language 'plpgsql';

create function insert_uv(varchar,varchar,varchar) returns integer as '
declare
   codeuv alias for $1;
   codetype alias for $2;
   libuv alias for $3;
   cletype integer;
begin
   select into cletype numtype(codeuv);
   insert into uv values (codeuv, cletype, libuv);
   return cletype;
end;
' language 'plpgsql';

When I do :

select insert_uv('SGBD','DUVC','TEST BD');
I get the following message :
ERROR:  insert or update on table "uv" violates foreign key constraint
"fk_uv_caracteri_type"
DETAIL:  Key (typnum)=(43) is not present in table "types".

I don't kown why.

Anyone has an idea ?

With best regards,
Patrice