2,951
edits
Array model: Difference between revisions
Jump to navigation
Jump to search
→External links
Miraheze>Marshall mNo edit summary |
|||
| (4 intermediate revisions by 3 users not shown) | |||
| Line 64: | Line 64: | ||
=== Numeric type coercion === | === Numeric type coercion === | ||
Most APLs, flat or nested, implicitly store simple numeric arrays as one of many [[numeric type]]s. When a numeric array is formed from numbers with different types, all numbers are converted to a common type in order to be represented as a flat array. If the hierarchy of numeric types is not strict, that is, there are some pairs of numeric types for which neither type is a subset of the other, then this coercion may affect the behavior of the numbers in the array. For example, [[J]] on a 64-bit machine uses both 64-bit integers and [[wikipedia:IEEE_754|double-precision floats]]. [[Catenate|Catenating]] the two results in an array of doubles, which will lose precision for integers whose absolute value is larger than 2<sup>53</sup>. In [[Dyalog APL]] a similar issue occurs with [[decimal | Most APLs, flat or nested, implicitly store simple numeric arrays as one of many [[numeric type]]s. When a numeric array is formed from numbers with different types, all numbers are converted to a common type in order to be represented as a flat array. If the hierarchy of numeric types is not strict, that is, there are some pairs of numeric types for which neither type is a subset of the other, then this coercion may affect the behavior of the numbers in the array. For example, [[J]] on a 64-bit machine uses both 64-bit integers and [[wikipedia:IEEE_754|double-precision floats]]. [[Catenate|Catenating]] the two results in an array of doubles, which will lose precision for integers whose absolute value is larger than 2<sup>53</sup>. In [[Dyalog APL]] a similar issue occurs with [[decimal float]]s and [[complex number]]s: combining the two results in an array of complex numbers, but this loses precision since Dyalog's complex numbers are stored as pairs of double-precision floats and its 128-bit decimal floats have higher precision that doubles. | ||
== Array characteristics == | == Array characteristics == | ||
| Line 95: | Line 95: | ||
* [http://help.dyalog.com/latest/index.htm#Language/Introduction/Variables/Arrays.htm Dyalog array model] | * [http://help.dyalog.com/latest/index.htm#Language/Introduction/Variables/Arrays.htm Dyalog array model] | ||
* [https://chat.stackexchange.com/rooms/52405/conversation/lesson-1-introduction-to-arrays-in-apl APL Cultivation] | * [https://chat.stackexchange.com/rooms/52405/conversation/lesson-1-introduction-to-arrays-in-apl APL Cultivation] | ||
{{APL | * [https://www.sacrideo.us/tag/apl-a-day/ APL a Day] series | ||
* [https://www.jsoftware.com/papers/array.htm What is an Array?] by [[Roger Hui]] (in [[J]]) | |||
{{APL features}} | |||