met_or_resp.erl

-module(met_or_resp).

-export([whatdo/1]).

-type diagnosis() :: metabolic_acidosis |
                     respiratory_acidosis |
                     respiratory_alkalosis |
                     metabolic_acidosis_respiratory_alkalosis |
                     metabolic_acidosis_respiratory_acidosis |
                     respiratory_acidosis_metabolic_alkalosis |
                     respiratory_acidosis_metabolic_acidosis.

-record(body_chem, {
          paco2 :: non_neg_integer(),
          hco3  :: non_neg_integer()
         }).

-define(PACOGOOD, 10).
-define(HCOGOOD, 10).

%%%===================================================================
%%% API
%%%===================================================================

-spec whatdo(#body_chem{}) -> diagnosis() | {error, patient_is_witch}.
whatdo(B=#body_chem{paco2=P, hco3=H}) when P > ?PACOGOOD, H > ?HCOGOOD ->
    case inc(hco_cmp_paco, B) of
        eq -> respiratory_acidosis;
        gt -> respiratory_acidosis_metabolic_alkalosis;
        lt -> respiratory_acidosis_metabolic_acidosis
    end;
whatdo(B=#body_chem{paco2=P, hco3=H}) when P =< ?PACOGOOD, H =< ?HCOGOOD ->
    case inc(paco_cmp_hco, B) of
        eq -> metabolic_acidosis;
        gt -> metabolic_acidosis_respiratory_alkalosis;
        lt -> metabolic_acidosis_respiratory_acidosis
    end;
whatdo(_) ->
    {error, patient_is_witch}.

%%%===================================================================
%%% Internal Functions
%%%===================================================================

inc(hco_cmp_paco, #body_chem{paco2=P, hco3=H}) ->
    cmp(H, P);
inc(paco_cmp_hco, #body_chem{paco2=P, hco3=H}) ->
    cmp(P, H).

cmp(X, Y) when X > Y -> gt;
cmp(X, Y) when X < Y -> lt;
cmp(X, X) -> eq.