Lua sort table value ascending - sorting

Question

I have a table I need to sort sel_notes[i].Pitch to ascending order.
These are the selected midi notes in a midi editor.
sel notes table :
sel_notes = {}
sel_notes[pitch] = {Pitch = pitch, Idx = i}
sel_notes[i] = {Pitch = pitch, Idx = i}
sel_notes table gives this using table.save-1.0.lua:
return {
-- Table: {1}
{
[64]={2},
[65]={3},
[66]={4},
[67]={5},
[52]={6},
[69]={7},
[68]={8},
[55]={9},
[56]={10},
[57]={11},
[58]={12},
[59]={13},
[60]={14},
[61]={15},
[62]={16},
[63]={17},
},
-- Table: {2}
{
["Pitch"]=63,
["Idx"]=64,
},
-- Table: {3}
{
["Pitch"]=52,
["Idx"]=65,
},
-- Table: {4}
{
["Pitch"]=58,
["Idx"]=66,
},
-- Table: {5}
{
["Pitch"]=52,
["Idx"]=67,
},
-- Table: {6}
{
["Pitch"]=52,
["Idx"]=67,
},
-- Table: {7}
{
["Pitch"]=58,
["Idx"]=69,
},
-- Table: {8}
{
["Pitch"]=63,
["Idx"]=68,
},
-- Table: {9}
{
["Pitch"]=52,
["Idx"]=55,
},
-- Table: {10}
{
["Pitch"]=58,
["Idx"]=56,
},
-- Table: {11}
{
["Pitch"]=63,
["Idx"]=57,
},
-- Table: {12}
{
["Pitch"]=58,
["Idx"]=69,
},
-- Table: {13}
{
["Pitch"]=63,
["Idx"]=59,
},
-- Table: {14}
{
["Pitch"]=52,
["Idx"]=60,
},
-- Table: {15}
{
["Pitch"]=52,
["Idx"]=61,
},
-- Table: {16}
{
["Pitch"]=63,
["Idx"]=62,
},
-- Table: {17}
{
["Pitch"]=63,
["Idx"]=68,
},
}
I need the table sorted so if I do this
for 1 = 1, 15 do
note = sel_notes[i].Pitch
index = sel_notes[i].Idx
print(note,index)
end
I will get this:
52 55
52 60
52 61
52 65
52 67
58 56
58 58
58 63
58 66
58 69
63 57
63 59
63 62
63 64
63 68
So then I'll be able to change the pitch value of the notes so they match the pitch value of another table that has the chord notes.
So:
pitch 52 to 55
pitch 58 to 59
pitch 63 to 62

Answer 1

You can use the table.sort method.
The first argument is a table and the second (optional) is a function that returns whether its first argument is smaller than the second.
Of course there's the problem of the rather weird table structure, so you need to get rid of the first element, which is meaningless. The easiest way for doing this would be using table.remove.
So something like
local function sort(tab)
table.remove(tab, 1) -- Remove first element
table.sort(tab, function(a, b)
return true -- Your sorting criterion goes here
end)
end