TasukiGap

Three-bar continuation pattern. Two same-coloured candles open a body gap in the trend direction, then an opposite-coloured candle opens inside the second body and closes back into the gap without filling it. The surviving gap says the trend is only pausing, not turning.

Quick reference

Field	Value
Family	Candlestick Patterns
Input type	Candle (uses open, close; high/low validated by Candle)
Output type	f64 — +1.0 upside, -1.0 downside, 0.0 otherwise
Output range	{-1.0, 0.0, +1.0}
Default parameters	none — TasukiGap::new()
Warmup period	3 (first two bars always 0.0)
Interpretation	Trend continuation; the unfilled gap confirms the prevailing move

Formula

Upside (+1.0):
  bar1 white, bar2 white
  upside body gap:            open2 > close1
  bar3 black, opens in body:  open2 < open3 < close2
  bar3 closes in the gap:     close1 < close3 < open2

Downside (-1.0): the mirror with black candles and a downside gap
  bar1 black, bar2 black,     open2 < close1
  bar3 white, opens in body:  close2 < open3 < open2
  bar3 closes in the gap:     open2 < close3 < close1

The third candle reaches into the gap but does not close past it: an upside setup needs close3 > close1 (gap survives) — a close back under close1 fills the gap and the pattern does not fire. Thresholds use exact body-edge comparisons (geometric house style, no rolling averages). See crates/wickra-core/src/indicators/tasuki_gap.rs.

Parameters

None. Constructed with TasukiGap::new().

Signed ±1 encoding

This pattern emits the uniform candlestick sign convention shared across the family — +1.0 upside (bullish continuation), −1.0 downside (bearish continuation), 0.0 no pattern — so it drops straight into a machine-learning feature matrix where the two directions occupy a single dimension.

Inputs / Outputs

use wickra::{Indicator, TasukiGap, Candle};
// TasukiGap: Input = Candle, Output = f64
const _: fn(&mut TasukiGap, Candle) -> Option<f64> = <TasukiGap as Indicator>::update;

• Always emits a value. The detector never returns None: warmup bars and no-match bars both return 0.0.
• Node. update(open, high, low, close) returns number; batch(open, high, low, close) returns Array<number>.
• Python. update(candle) returns float; batch(open, high, low, close) returns a 1-D numpy.ndarray (0.0 on warmup / no-match, never NaN).

Warmup

warmup_period() == 3. The first two bars return 0.0 because the three-bar window is not yet filled — pinned by first_two_bars_return_zero and the metadata test accessors_and_metadata.

Edge cases

• Filled gap. A third candle that closes through the gap is a reversal, not a tasuki — up_third_close_not_in_gap_yields_zero / down_third_close_not_in_gap_yields_zero pin the 0.0.
• Open outside the second body. The third candle must open within the second real body (up_third_open_outside_body_yields_zero).
• Wrong third colour. The third candle must oppose the first two (up_third_not_black_yields_zero / down_third_not_white_yields_zero).
• No gap. Without a body gap between bars 1 and 2 there is nothing to hold (up_no_gap_yields_zero / down_no_gap_yields_zero).
• Mixed leading colours. Bars 1 and 2 differing in colour yields 0.0 (mixed_colours_yield_zero).
• Reset. reset() clears the two-bar cache (reset_clears_state).

Examples

Rust

use wickra::{Candle, Indicator, TasukiGap};

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut t = TasukiGap::new();
    println!("{:?}", t.update(Candle::new(10.0, 11.2, 9.8, 11.0, 1.0, 0)?));   // white
    println!("{:?}", t.update(Candle::new(12.0, 14.0, 11.9, 13.5, 1.0, 1)?));  // white, gaps up
    println!("{:?}", t.update(Candle::new(13.0, 13.1, 11.4, 11.5, 1.0, 2)?));  // black, into gap
    Ok(())
}

Output:

Some(0.0)
Some(0.0)
Some(1.0)

The third candle is black, opens at 13.0 inside the second body (12, 13.5), and closes at 11.5 inside the gap (11, 12) — an upside tasuki gap. This matches the upside_tasuki_gap_is_plus_one unit test.

Python

import numpy as np
import wickra as ta

o = np.array([10.0, 12.0, 13.0])
h = np.array([11.2, 14.0, 13.1])
l = np.array([9.8,  11.9, 11.4])
c = np.array([11.0, 13.5, 11.5])

print(ta.TasukiGap().batch(o, h, l, c))  # [0. 0. 1.]

Node

const ta = require('wickra');
const t = new ta.TasukiGap();
t.update(10, 11.2, 9.8, 11);     // 0
t.update(12, 14, 11.9, 13.5);    // 0
console.log(t.update(13, 13.1, 11.4, 11.5)); // 1

Streaming

use wickra::{Candle, Indicator, TasukiGap};

let mut t = TasukiGap::new();
let candle_stream: Vec<wickra::Candle> = Vec::new(); // your live OHLCV candle feed
for bar in candle_stream {
    match t.update(bar) {
        Some(1.0)  => { /* upside gap holds — uptrend continuation */ }
        Some(-1.0) => { /* downside gap holds — downtrend continuation */ }
        _ => {}
    }
}

Interpretation

1. Stay-with-trend signal. Inside an uptrend the upside tasuki gap is a one-bar pause: the counter-coloured candle dips into the gap but fails to close it, so the prior gap-up still anchors the move. The downside variant is the mirror inside a downtrend.
2. Not a reversal. Unlike engulfing or piercing patterns, tasuki gaps argue for continuation. Read a filled gap (which this detector suppresses) as the warning sign instead.
3. Confirm the trend. Because the pattern is direction-agnostic about context, pair it with a trend filter (e.g. price above a rising Ema) so a "continuation" is continuing something real.

Common pitfalls

• Treating it as a reversal. The opposite-coloured third candle looks like a turn but the held gap means continuation.
• Ignoring the gap rule. A near-miss where the third candle closes a hair past the gap edge does not qualify — the comparison is strict.
• No trend context. In a flat range, gaps are noise; the pattern is only meaningful within an established trend.

References

• Steve Nison, Japanese Candlestick Charting Techniques (1991).

See also

• UpsideGapThreeMethods — gap continuation where the third candle does partly fill the gap.
• GapSideBySideWhite — twin white candles after an upside gap.
• Indicators-Overview — the full taxonomy.