I-Beam (`⌶`)¶

Syntax¶

  (⌶'module.function') Y        ⍝ monadic call
X (⌶'module.function') Y        ⍝ dyadic call

The operand is a string naming a Python callable in module.function form.

Description¶

⌶ is a monadic operator that derives a function from a Python callable. The derived function passes its APL arguments directly to the Python function.

Contract¶

The Python function must:

Accept one APLArray argument (monadic) or two APLArray arguments (dyadic, left then right).
Return an APLArray.

If the Python function raises an exception, MARPLE wraps it as a DOMAIN ERROR. If it returns something other than APLArray, MARPLE raises DOMAIN ERROR.

Examples¶

Given a Python file mylib.py:

from marple.arraymodel import APLArray, S

def double(right: APLArray) -> APLArray:
    return APLArray(list(right.shape), [x * 2 for x in right.data])

You can call it from MARPLE:

      (⌶'mylib.double') 1 2 3
2 4 6

The standard library uses i-beam internally:

      (⌶'marple.stdlib.str_impl.upper') 'hello'
HELLO

Security¶

By default, any importable Python module can be called via ⌶.

To restrict access, set the MARPLE_IBEAM_ALLOW environment variable to a comma-separated list of allowed module prefixes:

MARPLE_IBEAM_ALLOW=marple.stdlib,myproject

With this setting, only paths starting with marple.stdlib or myproject are allowed. All other paths raise SECURITY ERROR.

I-Beam (⌶)¶