create table from two input tables .output table's key will be from first input and values will be from second input table

Question

I am having a table in which I am passing names:

names = {'Sachin', 'Ponting', 'Dhoni'}

and in other table I am passing country names:

country = {"India", "Australia", "India"}

I want output table like:

out_table = {Sachin="India", Ponting="Australia", Dhoni="India"}

score 2 · Answer 1 · answered Nov 14 '13 at 06:13

2

You can make a new iterator that get values from both sequences:

function both_values(t1, t2)
    local i = 0
    return function() i = i + 1; return t1[i], t2[i] end
end

Then use the iterator like this:

local out_table = {}
for v1, v2 in both_values(names, country) do
    out_table[v1] = v2
end

answered Nov 14 '13 at 06:13

Yu Hao

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It is giving error . stdin:2: attempt to index global `out_table' (a nil value) – Prashant Gaur Nov 14 '13 at 06:24
@PrashantGaur Are you testing the program in the Lua interpreter line by line? If so, declare `out_table` as global, i.e, `out_table = {}` without `local`. – Yu Hao Nov 14 '13 at 06:34
why this ? can you explain i am new to lua – Prashant Gaur Nov 14 '13 at 06:41
3

@PrashantGaur Because in interactive mode, each line is a chunk by itself (unless it is incomplete). When you entered the next line, the previous local declaration is out of scope. – Yu Hao Nov 14 '13 at 06:49

score 2 · Accepted Answer · answered Nov 14 '13 at 06:36

Here's a straight-forward attempt:

names = {'Sachin', 'Ponting', 'Dhoni'}
countries = {"India", "Australia", "India"}

function table_map(names, countries)
    local out = {}
    for i, each in ipairs(names) do
        out[each] = countries[i]
    end
    return out
end

out_table = table_map(names, countries)

Live repl demo.

create table from two input tables .output table's key will be from first input and values will be from second input table

2 Answers2