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RC2_STATE_EMPTY_LIST

A bare [] literal has no element type to infer.

What it means

A class-body list declared as name = [] carries no element-type information. RaamCode can’t tell whether the list holds ints, decimals, bools, or strings — and the slot has to be typed before the first bar runs.

Why it happens

class Bad(Strategy):
    trade = Symbol()
    sizing = FixedCapital()


    empty = []          # ❌ — what's the element type?


    def execute(self):
        if self.trade.is_flat:
            self.buy(self.trade)

How to fix it

Pin the element type with the [<literal>]*0 idiom — the literal in the brackets fixes the type, *0 gives it zero length.

class Good(Strategy):
    trade = Symbol()
    sizing = FixedCapital()


    no_decimals = [0.0]*0    # ✅ empty list of decimal
    no_ints = [0]*0          # ✅ empty list of int
    no_flags = [False]*0     # ✅ empty list of bool
    no_words = [""]*0        # ✅ empty list of string


    def execute(self):
        if self.trade.is_flat:
            self.buy(self.trade)

Or, when the contents are known up front, write them out:

class Prefilled(Strategy):
    trade = Symbol()
    sizing = FixedCapital()


    nq_highs = [0.0, 0.0, 0.0, 0.0, 0.0]   # ✅ five decimals
    # equivalently: nq_highs = [0.0]*5


    def execute(self):
        self.nq_highs[0] = self.trade.high
        if self.trade.is_flat:
            self.buy(self.trade)

Why we don’t allow bare []

Each list is pinned to a single element type by the literal you declare. An empty literal offers nothing to pin to, and inferring one would mean either a silent default (“always decimal”) or a guess from the first write — both add ambiguity for no benefit. [0.0]*0 is three characters longer and removes it entirely.