Stack binding

A call can receive Video or Audio values explicitly through arguments or implicitly from the accessible stack.

Scalar arguments

Positional scalar values bind parameters in declaration order. Named scalar arguments use =:

image("title.png", duration=2s, fit=contain)

Positional graph expressions

A graph-producing positional expression behaves like a preceding statement in the current stack frame:

flash_cut(
    image("before.png", 2s),
    image("after.png", 2s),
    160ms,
)

is equivalent to:

image("before.png", 2s)
image("after.png", 2s)
flash_cut(160ms)

ClipAsm evaluates the expressions in source order.

Implicit stack inputs

If a call omits graph inputs, ClipAsm selects accessible values by exact type. For fixed inputs, it works from the program’s last input to its first and takes the nearest matching occurrence for each.

A variadic program such as concat consumes every accessible value of the selected Video or Audio type in physical stack order. Values of another type stay where they are.

Use <Video> or <Audio> when both generic choices are possible.

Named graph inputs

ClipAsm evaluates a named graph input in an isolated input body:

set_audio(
    video=video("picture.mp4"),
    audio=audio("sound.wav"),
)

It supplies that input directly and does not consume a value from the caller’s stack. A named graph input must produce exactly one value of the required type.

Do not mix positional graph expressions and named graph inputs in one call. Named scalar arguments may still accompany positional graph expressions.

Ownership and visibility

@owned allows a call to consume only occurrences created by the current body. @visible may also reach occurrences created by enclosing bodies, stopping at the nearest owned boundary.

Most direct built-ins and imported programs default to owned access. join and during default to visible access. The setting applies to one invocation and does not automatically propagate into its body.

@owned {
    image("inside.png", 1s)
    @visible concat
}

The owned block prevents the inner visible call from reaching values outside the block.

See Stack values, ownership, and visibility for an example-led explanation.