Shark

Five-point (X-A-B-C-D) harmonic distinguished by an expansion leg (AB longer than XA) and a 0.886–1.13 D completion near A. Bullish (D a swing low) → +1, bearish → -1.

Quick reference

Item	Value
Family	Harmonic Patterns
Input type	Candle (uses high, low)
Output type	f64 (+1 / -1 / 0)
Output range	{-1.0, 0.0, +1.0}
Default parameters	none (swing threshold 5%, baked)
Warmup period	6
Interpretation	Reversal at the D completion

Formula

last five pivots X-A-B-C-D (the 5-point reading of the Shark):
  AB / XA ∈ [1.13, 1.618]  (expansion — B overshoots X)
  BC / AB ∈ [1.618, 2.24]
  CD / BC ∈ [0.382, 0.886]
  AD / XA ∈ [0.886, 1.13]  (the defining D completion near A)
direction: D a swing low → +1, a swing high → -1

See crates/wickra-core/src/indicators/shark.rs.

Parameters

None. Swing threshold 0.05 is a baked-in family constant (pattern_swing.rs); the Fibonacci windows are documented detector constants. Shark::new is infallible.

Inputs / Outputs

const _: fn(&mut wickra::Shark, wickra::Candle) -> Option<f64> =
    <wickra::Shark as wickra::Indicator>::update;

• Python. update((o,h,l,c,v,ts)) → float (never None); batch(open, high, low, close) → 1-D ndarray.
• Node. update(open, high, low, close) → number; batch(open, high, low, close) → number[].
• WASM. update(open, high, low, close) → number.

Warmup

warmup_period() == 6. Five confirmed pivots are required. Pinned by test accessors_and_metadata.

Edge cases

• Bullish Shark reports +1 (test bullish_shark_is_plus_one).
• Bearish Shark reports -1 (test bearish_shark_is_minus_one).
• Legs outside the windows report 0.0 (test out_of_ratio_does_not_trigger).
• reset clears state (test reset_clears_state).
• Streaming equals batch (test batch_equals_streaming).

Examples

Rust

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

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let bars = [
        (149.85, 150.0, 149.85, 149.85),
        (100.0, 148.5, 100.0, 100.0),
        (101.0, 140.0, 101.0, 101.0),
        (88.0, 138.6, 88.0, 88.0),
        (88.88, 186.8, 88.88, 88.88),
        (100.0, 184.932, 100.0, 100.0),
        (101.0, 110.0, 101.0, 101.0), // D confirms → bullish
    ];
    let mut pat = Shark::new();
    let mut last = 0.0;
    for (ts, (o, h, l, c)) in bars.iter().enumerate() {
        last = pat.update(Candle::new(*o, *h, *l, *c, 1.0, ts as i64)?).unwrap();
    }
    println!("{last}"); // 1
    Ok(())
}

Python

import wickra as ta

bars = [
    (149.85, 150.0, 149.85, 149.85, 1.0, 0),
    (100.0, 148.5, 100.0, 100.0, 1.0, 1),
    (101.0, 140.0, 101.0, 101.0, 1.0, 2),
    (88.0, 138.6, 88.0, 88.0, 1.0, 3),
    (88.88, 186.8, 88.88, 88.88, 1.0, 4),
    (100.0, 184.932, 100.0, 100.0, 1.0, 5),
    (101.0, 110.0, 101.0, 101.0, 1.0, 6),
]
pat = ta.Shark()
print([pat.update(b) for b in bars][-1])  # 1.0

Node

const wickra = require('wickra');
const bars = [
  [149.85, 150.0, 149.85, 149.85], [100.0, 148.5, 100.0, 100.0],
  [101.0, 140.0, 101.0, 101.0], [88.0, 138.6, 88.0, 88.0],
  [88.88, 186.8, 88.88, 88.88], [100.0, 184.932, 100.0, 100.0],
  [101.0, 110.0, 101.0, 101.0],
];
const pat = new wickra.Shark();
let last = 0;
for (const [o, h, l, c] of bars) last = pat.update(o, h, l, c);
console.log(last); // 1

Streaming

pat = ta.Shark()
for o, h, l, c, v, ts in candle_feed:
    signal = pat.update((o, h, l, c, v, ts))
    if signal != 0:
        pass  # Shark completed at D — reversal setup

Interpretation

1. Expansion structure. The Shark is unusual in that B overshoots X (AB > XA); the detector reads it as a 5-point XABCD with the expansion encoded in the AB/XA > 1 window.
2. Near-A completion. D returns close to A (0.886–1.13 of XA), a tighter reversal zone than the Crab/Butterfly extensions.

Common pitfalls

• 5-point approximation. Some literature defines the Shark on the O-X-A-B-C points; this detector uses the equivalent 5-pivot XABCD reading, documented in the source.
• Confirmation lag. Non-repainting but lags the visual D.

References

• Carney, S. Harmonic Trading, Volume Two (2013) — the Shark pattern.

See also

• Cypher, Crab, Gartley.
• Indicators-Overview — full taxonomy.