Question

I have seen code in lua like this

if (a==b or false) then

what is the purpose of the “or false”?

This is the original code:

        Function = function(self, aura, auraID)
        -- Store the version.
        -- aura.Version = 50000;
        -- Fix texmode/glow.
        aura.texmode = (aura.texmode == 1 or aura.texmode == true or false);
        -- Texture source.
        if(aura.owntex or aura.SourceType == PowaAuras.SourceTypes.Icon) then
            aura.SourceType = PowaAuras.SourceTypes.Icon;
        elseif(aura.wowtex or aura.SourceType == PowaAuras.SourceTypes.WoW) then
            aura.SourceType = PowaAuras.SourceTypes.WoW;
        elseif(aura.customtex or aura.SourceType == PowaAuras.SourceTypes.Custom) then
            aura.SourceType = PowaAuras.SourceTypes.Custom;
        elseif(aura.textaura or aura.SourceType == PowaAuras.SourceTypes.Text) then
            aura.SourceType = PowaAuras.SourceTypes.Text;
        else
            aura.SourceType = PowaAuras.SourceTypes.Default;
        end

    end

And here is another example

            -- Iterate over element children.
        visible, hidden = self:UpdateScrollList(key, level+1, visible, hidden, 
            (parentShowing == true and item:GetExpanded() or false));

Answer 1

This looks like a behavior that comes from the syntax:

a=b or false

to initialize a to the value of b or false if b isn’t defined.

Within the if statement as you wrote it, I don’t see any purpose since the == is evaluated before the or. If they used parenthesis to change the order of operations, then it could be used to validate that b has been defined, e.g.:

> a=nil
> b=nil
> if (a == (b or false)) then print("yikes") else print("aok") end
aok
> if (a == b or false) then print("yikes") else print("aok") end
yikes