Complex (function)
⌾

Complex (⌾
) is a dyadic scalar function which combines its arguments into a complex number having with the left argument as real part and the right argument as imaginary part. It was added to J as j.
together with initial support for complex numbers, and was adopted in Extended Dyalog APL using the glyph ⌾
because it was seen as a type of numerical composition (∘
) for the circular (○
) domain. Complex shares its glyph with Imaginary which is equivalent to applying Complex with a left argument of 0.
The question of whether to include this function is one of Roger Hui's 50 exercises in APL language design^{[1]}:
Complex numbers can be constructed as ordered pairs of real numbers, similar to how integers can be constructed as ordered pairs of natural numbers and rational numbers as ordered pairs of integers. For complex numbers,
j.
plays the same role as
for integers and÷
for rational numbers.
Examples
¯2 9 5 ⌾ 3 ¯4 6
¯2J3 9J¯4 5J6
Documentation
 J Dictionary, NuVoc