Why does thinkscript throw these issues when I try to create a counter? - thinkscript

Question

When I try to create a counter and increment it in an if-else statement the thinkscript compiler throws confusing errors which tell me it's not allowed, yet I've seen this done in several examples. They even have a reserved word: rec in order to allow for incrementing counters.
score = score + 1; produces: # Already assigned: Score at...
rec score = score + 1; produces: # identifier already used: score at ...
# not allowed inside an IF/THEN/ELSE statement
#
# TD Ameritrade IP Company, Inc. (c) 2017-2019
#
input price = close;
input length = 9;
input displace = 0;
def score = 0;
def smavrgg = Average(price[-displace], length);
def expMvAvrg = ExpAverage(price[-displace], length);
plot SMA = smavrgg;
SMA.SetDefaultColor(GetColor(1));
plot AvgExp = expMvAvrg;
AvgExp.SetDefaultColor(GetColor(1));
# 1 if uptrend, 0 if downtrend
def lastTrendisUp = (close[0] - close[1]) > 0 ;
def secondLastTrendisUP = (close[1] - close[2]) > 0;
def thirdLastTrendisUP = (close[2] - close[3]) > 0;
def fourthLastTrendisUP = (close[3] - close[4]) > 0;
input lookback = 5;
# defines intBool (array) that indicates whether one or the other crossed.
def bull_cross = SMA crosses above AvgExp;
def bear_cross = AvgExp crosses below SMA;
# returns the highest value in the data array for the lookback.
# so [0, 1, 0, 0] means a cross happened within the last units. and 1 will be returned.
if (bull_cross[0] or bear_cross[0]) then {
if lastTrendisUp {
# Already assigned: Score at...
score = score + 1;
# identifier already used: score at ...
# not allowed inside an IF/THEN/ELSE statement
rec score = score + 1;
} else {
}
} else if (bull_cross[1] or bear_cross[1]) {
if secondLastTrendisUP {
} else {
}
} else if (bull_cross[2] or bear_cross[2]) {
if thirdLastTrendisUP {
} else {
}
} else if (bull_cross[3] or bear_cross[3]) {
if fourthLastTrendisUP {
} else {
}
} else if (bull_cross[4] or bear_cross[4]) {
} else {
}
# If most recent cross happened in the last 4
# and most recent cross occured on a green candle.
def bull_lookback = Highest(bull_cross, lookback);
def bear_lookback = Highest(bear_cross, lookback);
# def think = if bull_lookback or bear_lookback
plot signal = if bull_lookback then 2 else if bear_lookback then 1 else 0;
signal.AssignValueColor(if signal == 2 then Color.DARK_GREEN else if signal == 1 then Color.DARK_RED else Color.DARK_ORANGE);
AssignBackgroundColor(if signal == 2 then Color.DARK_GREEN else if signal == 1 then Color.DARK_RED else Color.DARK_ORANGE);

Answer 1

Once you define a variable in Thinkscript and assign it, it's only valid for one bar, it behaves as a constant so it can't be reassigned. I'm pretty sure you can't even place a Def command into a conditional, just like in most codes. In order to create a 'dynamic' SCORE, you need to assign the dynamic value in the same line you instantiate. You don't need
def score = 0;
since when you define the variable, it will have a zero value anyway.
You also don't the extra variables for the 'trendisup' placeholders, because really
secondLastTrendisUp
is the same as saying
lastTrendisUp[1]
because it was already computed in the last bar.
You can accomplish the counter without the extra variables using a FOLD statement, like this:
def score= fold index=0 to 4
with p=0
do p + ((bearcross[index] or bullcross[index]) and lastTrendisUp[index]);
This will add one to the score each time the conditions are true, and assign the total to the SCORE variable. I think this is what you would like to accomplish, I can't tell, since you never show what you're doing with the score variable later on... If you are looking to just find out if bullcross or bearcross condition and also the lasttrendisup condition evaluates to true in any of the last five bars, then you add 'while p=0' above the with, and it will return a one to SCORE as soon as it encounters the first true instance.

Answer 2

counter to increase a variable by 1, on each bar:
score = score[1] + 1;
the [1] means, go get the value from that variable from 1 bar ago.

Answer 3

The answer is that variables in thinkscript cannot be changed.