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Conditionals & Logic

Signal-rate decision-making: compare signals, combine boolean signals with AND/OR/NOT, and pick between two signals based on a condition. Every operation runs sample-by-sample at audio rate.

Truth convention

  • A signal value is truthy when it is greater than 0.0. Anything <= 0.0 is falsy (including 0, -0, and negative numbers).
  • Comparison and logic operators output exactly 1.0 for true and 0.0 for false.
  • Equality (eq, neq, ==, !=) uses an epsilon of 1e-6 so floating-point round-off does not produce false negatives.

All operators below are also available as infix syntax; see Operators for the precedence table.

select

Select - Choose between two signals based on a condition.

ParamTypeDefaultDescription
condsignal-Condition signal: picks a when cond > 0, otherwise b
asignal-Output when cond is truthy
bsignal-Output when cond is falsy

Sample-by-sample mux. There is no infix ternary syntax; use select(cond, a, b).

// Switch oscillators on a gate pattern
gate = n"1 0 1 0"
select(gate, saw(440), sqr(220)) |> out(@)
// Apply distortion only when the input is loud
sig = saw(110)
select(sig > 0.5, dist(sig, 4), sig) |> out(@)

gt

Greater Than - Outputs 1.0 when a > b, otherwise 0.0.

ParamTypeDefaultDescription
asignal-First operand
bsignal-Second operand

Equivalent to the > operator.

// Square wave from a sine via threshold
sine(440) > 0 |> out(@)

lt

Less Than - Outputs 1.0 when a < b, otherwise 0.0.

ParamTypeDefaultDescription
asignal-First operand
bsignal-Second operand

Equivalent to the < operator.

// Open the filter only on quiet sections
freq = lfo(0.25) * 2000 + 200
saw(110) |> lp(@, freq * (freq < 1000)) |> out(@)

gte

Greater or Equal - Outputs 1.0 when a >= b, otherwise 0.0.

ParamTypeDefaultDescription
asignal-First operand
bsignal-Second operand

Equivalent to the >= operator.

// Hold a gate above a threshold
amp = lfo(0.5)
gate = gte(amp, 0.5)
sine(440) * gate |> out(@)

lte

Less or Equal - Outputs 1.0 when a <= b, otherwise 0.0.

ParamTypeDefaultDescription
asignal-First operand
bsignal-Second operand

Equivalent to the <= operator.

sine(440) * lte(lfo(0.5), 0) |> out(@)

eq

Approximate Equality - Outputs 1.0 when |a - b| < 1e-6, otherwise 0.0.

ParamTypeDefaultDescription
asignal-First operand
bsignal-Second operand

Equivalent to the == operator. The epsilon protects against floating-point drift: values like 0.1 + 0.2 and 0.3 compare equal.

// Trigger only on exact step matches
freq = n"c4 e4 g4 c5" |> @freq
hit = eq(freq, 261.6)  // 1.0 only on c4 (~261.6 Hz)

neq

Approximate Inequality - Outputs 1.0 when |a - b| >= 1e-6, otherwise 0.0.

ParamTypeDefaultDescription
asignal-First operand
bsignal-Second operand

Equivalent to the != operator. The exact inverse of eq (same epsilon).

// Drop a voice on the rest steps only
freq = n"c4 ~ g4 c5" |> @freq
voice = saw(freq) * neq(freq, 0)
voice |> out(@)

band

Logical AND - Outputs 1.0 when both inputs are truthy (> 0), otherwise 0.0.

ParamTypeDefaultDescription
asignal-First operand
bsignal-Second operand

Equivalent to the && operator.

// Accent only when both gates fire
loud = lfo(0.5) > 0.5
hit  = trigger(4)
band(loud, hit) |> ar(@, 0.005, 0.1) |> out(@)

bor

Logical OR - Outputs 1.0 when at least one input is truthy, otherwise 0.0.

ParamTypeDefaultDescription
asignal-First operand
bsignal-Second operand

Equivalent to the || operator.

// Layer two rhythmic patterns into one gate
g1 = n"1 0 0 0"
g2 = n"0 0 1 0"
combined = bor(g1, g2)  // "1 0 1 0"

bnot

Logical NOT - Outputs 1.0 when the input is falsy (<= 0), otherwise 0.0.

ParamTypeDefaultDescription
asignal-Input

Equivalent to the prefix ! operator.

// Inverse gate, sustain when no trigger
gate = trigger(4)
sustain = bnot(gate)
sine(220) * sustain |> out(@)

See also