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Variant dates back all the way to [[Iverson notation]] where a subscript was used to indicate which [[index origin]] a [[primitive]] would operate under. This system was dropped in [[APL\360]]. Instead, the [[system command]] <source lang=apl inline>)ORIGIN</source> was provided for controlling the interpreter's global setting. This was then supplemented with a [[system variable]] to control the global state. Though this feature is still present in many APL systems, together with numerous other system variables for controlling other aspects of the system, for example [[comparison tolerance]], these global settings were recognised as an unfortunate design in that every programmer would be forced to set and localise every system variable that could affect the given code. Later, [[Ken Iverson]] envisioned a return to a per-invocation setting, similar to the original notation, but this time in the form of a dyadic operator that would customise [[primitive function]]s. | Variant dates back all the way to [[Iverson notation]] where a subscript was used to indicate which [[index origin]] a [[primitive]] would operate under. This system was dropped in [[APL\360]]. Instead, the [[system command]] <source lang=apl inline>)ORIGIN</source> was provided for controlling the interpreter's global setting. This was then supplemented with a [[system variable]] to control the global state. Though this feature is still present in many APL systems, together with numerous other system variables for controlling other aspects of the system, for example [[comparison tolerance]], these global settings were recognised as an unfortunate design in that every programmer would be forced to set and localise every system variable that could affect the given code. Later, [[Ken Iverson]] envisioned a return to a per-invocation setting, similar to the original notation, but this time in the form of a dyadic operator that would customise [[primitive function]]s. | ||
Although [[SHARP APL]] didn't implement Iverson's idea, [[J]] did. Later [[Dyalog APL 13.0]] (2011) repurposed it as a way of providing auxilliary arguments to [[system functions]] and [[derived function|functions derived]] from [[system operators]], but not for primitives. | |||
== Usage === | == Usage === | ||