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→History: Version number for APL2 conformability in Dyalog
(→History: NARS and APL2 negative number handling is different) |
(→History: Version number for APL2 conformability in Dyalog) |
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In 1980, [[Bob Bernecky]] introduced the extension Replicate to [[SHARP APL]]: he allowed an operand (since SHARP's Replicate is an operator) consisting of non-negative integers rather than just [[Boolean]]s to indicate the number of times to copy.<ref>[[Bob Bernecky|Bernecky, Bob]]. SATN-34: Replication. [[IPSA]]. 1980-08-15.</ref> This extension was rapidly and widely adopted, starting with [[NARS]] in 1981, and is now a feature of the [[ISO/IEC 13751:2001]] standard. | In 1980, [[Bob Bernecky]] introduced the extension Replicate to [[SHARP APL]]: he allowed an operand (since SHARP's Replicate is an operator) consisting of non-negative integers rather than just [[Boolean]]s to indicate the number of times to copy.<ref>[[Bob Bernecky|Bernecky, Bob]]. SATN-34: Replication. [[IPSA]]. 1980-08-15.</ref> This extension was rapidly and widely adopted, starting with [[NARS]] in 1981, and is now a feature of the [[ISO/IEC 13751:2001]] standard. | ||
Two extensions to allow negative numbers in the left argument have been introduced, in each case specifying that the negative of a number indicates that many [[fill element]]s should appear in the result. In 1981 [[NARS]] specified that these fill elements replace the corresponding right argument element, so that the lengths of the left and right arguments are always equal, and extended [[Expand]] similarly. [[APL2]], in 1984, made the opposite choice, so that the length of the right argument along the specified axis is equal to the number of non-negative elements on the left. [[APL2]] also loosened the [[conformability]] requirements further than simply allowing [[singleton extension]]: it allowed a right argument with length 1 along the replication axis to be extended. [[Dyalog APL]], created before APL2, adopted the [[NARS]] definition for negative elements | Two extensions to allow negative numbers in the left argument have been introduced, in each case specifying that the negative of a number indicates that many [[fill element]]s should appear in the result. In 1981 [[NARS]] specified that these fill elements replace the corresponding right argument element, so that the lengths of the left and right arguments are always equal, and extended [[Expand]] similarly. [[APL2]], in 1984, made the opposite choice, so that the length of the right argument along the specified axis is equal to the number of non-negative elements on the left. [[APL2]] also loosened the [[conformability]] requirements further than simply allowing [[singleton extension]]: it allowed a right argument with length 1 along the replication axis to be extended. [[Dyalog APL]], created before APL2, adopted the [[NARS]] definition for negative elements but added APL2 conformability extension in [[Dyalog APL 13.1|version 13.1]]. Later [[APLX]] took advantage of the fact that the two negative number extensions can be distinguished by the length of the left argument, and implemented every NARS and APL2 extension. | ||
[[A+]] and [[J]] modified Replicate to fit [[leading axis theory]]. Rather than allow Replicate to operate on any axis they have only one Replicate function (in A+, <source lang=apl inline>/</source>; in J, <source lang=j inline>#</source>) which works on the first axis—it copies [[major cell]]s rather than elements. Both languages rejected the [[NARS]] extension to negative left arguments, but J introduced its own system to add [[fill element]]s by allowing [[complex number]]s in the left argument, and removed the [[Expand]] function entirely. [[Arthur Whitney]] went on to make a more radical change in [[K]], removing Replicate entirely in favor of [[Where]]. | [[A+]] and [[J]] modified Replicate to fit [[leading axis theory]]. Rather than allow Replicate to operate on any axis they have only one Replicate function (in A+, <source lang=apl inline>/</source>; in J, <source lang=j inline>#</source>) which works on the first axis—it copies [[major cell]]s rather than elements. Both languages rejected the [[NARS]] extension to negative left arguments, but J introduced its own system to add [[fill element]]s by allowing [[complex number]]s in the left argument, and removed the [[Expand]] function entirely. [[Arthur Whitney]] went on to make a more radical change in [[K]], removing Replicate entirely in favor of [[Where]]. | ||