Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
Gains 100 ATK for each "Meklord" monster on the field, except this card. When this card is Normal Summoned: You can target 1 face-up monster your opponent controls; halve that target's ATK, until the end of this turn.
--機皇兵グランエル・アイン
--Meklord Army of Granel
local s,id=GetID()
function s.initial_effect(c)
	--atkup
	local e1=Effect.CreateEffect(c)
	e1:SetType(EFFECT_TYPE_SINGLE)
	e1:SetProperty(EFFECT_FLAG_SINGLE_RANGE)
	e1:SetRange(LOCATION_MZONE)
	e1:SetCode(EFFECT_UPDATE_ATTACK)
	e1:SetValue(s.val)
	c:RegisterEffect(e1)
	--atk down
	local e2=Effect.CreateEffect(c)
	e2:SetDescription(aux.Stringid(id,0))
	e2:SetCategory(CATEGORY_ATKCHANGE)
	e2:SetProperty(EFFECT_FLAG_CARD_TARGET)
	e2:SetType(EFFECT_TYPE_SINGLE+EFFECT_TYPE_TRIGGER_O)
	e2:SetCode(EVENT_SUMMON_SUCCESS)
	e2:SetTarget(s.target)
	e2:SetOperation(s.operation)
	c:RegisterEffect(e2)
end
s.listed_series={SET_MEKLORD}
function s.val(e,c)
	return Duel.GetMatchingGroupCount(aux.FaceupFilter(Card.IsSetCard,SET_MEKLORD),0,LOCATION_MZONE,LOCATION_MZONE,c)*100
end
function s.target(e,tp,eg,ep,ev,re,r,rp,chk,chkc)
	if chkc then return chkc:IsControler(1-tp) and chkc:IsFaceup() and chkc:IsLocation(LOCATION_MZONE) end
	if chk==0 then return Duel.IsExistingTarget(Card.IsFaceup,tp,0,LOCATION_MZONE,1,nil) end
	Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_FACEUP)
	Duel.SelectTarget(tp,Card.IsFaceup,tp,0,LOCATION_MZONE,1,1,nil)
end
function s.operation(e,tp,eg,ep,ev,re,r,rp)
	local tc=Duel.GetFirstTarget()
	if tc:IsFaceup() and tc:IsRelateToEffect(e) then
		local e1=Effect.CreateEffect(e:GetHandler())
		e1:SetType(EFFECT_TYPE_SINGLE)
		e1:SetCode(EFFECT_SET_ATTACK_FINAL)
		e1:SetReset(RESETS_STANDARD_PHASE_END)
		e1:SetValue(tc:GetAttack()/2)
		tc:RegisterEffect(e1)
	end
end