How to replace empty atoms with fresh variables in a dict?

Help! Predicate
1

Hi,

I am receiving dicts at runtime from reading a csv file, such as:

D = _{a:[1,2,'',4],b:[w,x,y,z]}.

Each list value corresponds to a column in the original csv. Empty atoms are missing values. I would like to replace each missing value with a distinct fresh variable. What is a good way of achieving that ?

My code for acquiring the dict:

:-use_module(library(csv)).
:-use_module(library(clpfd),[transpose/2]).

cdr([_|T],T).

csv_to_dict(File,Tag,Dict):-
    csv_read_file(File,[Header|Rows]),
    Header=..[row|Names],
    maplist(=..,Rows,D),
    maplist(cdr,D,Data),
    transpose(Data,Columns),
    pairs_keys_values(Pairs,Names,Columns),
    dict_create(Dict,Tag,Pairs).

Thanks !

2

Easiest is to do this after transforming the row to a list as you do that anyway. Now you can simply define

map_to_var('', _).

and call

maplist(map_to_var, List, WithVars).
2 Likes