Difference between revisions of "References and Data Structures"
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The result of Ref_to_M looks like this: | The result of Ref_to_M looks like this: | ||
| − | [[File:result_ref-to-m.png| | + | [[File:result_ref-to-m.png|300px]] |
You can double-click the cell containing «ref» to view the value referenced, in this case: | You can double-click the cell containing «ref» to view the value referenced, in this case: | ||
| − | [[File:result_ref-to-m2.png| | + | [[File:result_ref-to-m2.png|300px]] |
You can also create an array of references. Suppose: | You can also create an array of references. Suppose: | ||
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Ksquare → | Ksquare → | ||
| − | [[File:result-ksquare.png| | + | [[File:result-ksquare.png|300px]] |
Variable Ref_to_Ksquare | Variable Ref_to_Ksquare | ||
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If you click the «ref» cell, it opens: | If you click the «ref» cell, it opens: | ||
| − | [[File:result_ref_ksquare2.png| | + | [[File:result_ref_ksquare2.png|300px]] |
You can also create an array of references from an array, for example: | You can also create an array of references from an array, for example: | ||
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any of these cells to see what it refers to. | any of these cells to see what it refers to. | ||
| − | [[File:result_ref_ksquare_array.png| | + | [[File:result_ref_ksquare_array.png|300px]] |
Clicking the third cell, for example, gives: | Clicking the third cell, for example, gives: | ||
| − | [[File:result_ref_ksquare_array2.png| | + | [[File:result_ref_ksquare_array2.png|300px]] |
==Managing indexes of referenced subarrays: \[i, j,...] e== | ==Managing indexes of referenced subarrays: \[i, j,...] e== | ||
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\ [K] Ksquare → | \ [K] Ksquare → | ||
| − | [[File:result_ref_ksquare_array3.png| | + | [[File:result_ref_ksquare_array3.png|300px]] |
It creates a similar result to \ Ksquare, since K is the only index of Ksquare. | It creates a similar result to \ Ksquare, since K is the only index of Ksquare. | ||
Revision as of 15:11, 17 December 2015
A reference is an indirect link to a value, an atom or an array. A variable can contain a single reference to a value, or it can contain an array of references. Variables and arrays can themselves contain references, nested to any depth. This lets you create complex data structures, such as linked lists, trees, and non-rectangular structures. Use of references is provided by two operators:
- \e is the reference operation. It creates a reference to the value of expression e.
- #e is the dereference operation. It obtains the value referred to by e. If e is not a reference, it issues a warning and returns Null.
An example: Variable M Definition: 100
Variable Ref_to_M Definition: \ M
The result of Ref_to_M looks like this:
You can double-click the cell containing «ref» to view the value referenced, in this case:
You can also create an array of references. Suppose:
Index K Definition: 1..5
Variable Ksquare Definition: K^2
Ksquare →
Variable Ref_to_Ksquare Definition: \ Ksquare
Ref_to_Ksquare →
If you click the «ref» cell, it opens:
You can also create an array of references from an array, for example:
Variable Ref_Ksquare_array Definition: \ [] Ksquare Ksquare →
The empty square brackets [ ] specify that the values referred to have no indexes, i.e., they are atoms. You can now click any of these cells to see what it refers to.
Clicking the third cell, for example, gives:
Managing indexes of referenced subarrays: \[i, j,...] e
More generally, you can list in the square brackets any indexes of e that you want to be indexes of each subarray referenced by the result. The other indexes of e (if any) are used as indexes for the referencing array. Thus, in the example above, since there were no indexes in square brackets, the index K was used as an index of the reference array. If instead we write:
\ [K] Ksquare →
It creates a similar result to \ Ksquare, since K is the only index of Ksquare.
To summarize:
\ e Creates a reference to the value of expression e, whether it is an atom or an array. \ [] e Creates an array indexed by all indexes of e containing references to all atoms from e. For x[i] := a DO e Assigns to loop variable xsuccessive subarrays from arraya, each indexed only byi. It repeats evaluation of expressionefor each index value ofaother thani. As before, the result has the same indexes asa.For x[i, j …] := a DO e Assigns to loop variable xsuccessive subarrays from arraya, each indexed only byi, j ….It repeats evaluation of expressionefor each index value ofaother thani, j ….. As before, the result has the same indexes asa.
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