SHARP APL

SHARP APL (later SAX: SHARP APL for UNIX) was a standalone version of APL offered by I.P. Sharp Associates (IPSA), who had previously offered APL interpretation as a timesharing service. IPSA employed many notable APL designers including Ken Iverson, and SHARP APL was the source of many developments in flat array theory. Notable features of SHARP APL include function rank, the Rank operator, and leading axis theory, as well as relative comparison tolerance and close composition operators including Under.

Scalar
All scalar functions have rank zero.

Numeric types
SHARP originally supported only real numbers using double (8-byte) precision. Numbers were stored in one of three types:
 * Boolean, with one bit per value
 * Integer, with four bytes per value
 * Floating, with eight bytes per value

SATN-40 describes the addition of complex numbers to SHARP APL.