chain->sort

chain ->sort: compare=[code|function], unique=[bool]

Sort the elements in the chain. Two elements are compared by examining the return status of the code object. Both @arg1 and @arg2 are bound to some element of the chain. Execution of the code is supposed to succeed if @arg1 must be before @arg2 in the sorted chain. If code is a function object, the return status is interpreted as follows:

integer smaller then 0 or the atom smaller @arg1 must be before @arg2
0 or the atom equal Both elements are equal (neither is deleted, but their order is undefined).
anything else @arg1 must be after @arg2
Common code objects to use are the arithmetic comparison objects and messages invoking a string comparison method. Examples:

Sort a chain of integers, lowest first:
```
send(Chain, sort, @arg1 < @arg2).
```
Sort a chain of char_array objects, alphabetically lowest first:
```
send(Chain, sort, ?(@arg1, compare, @arg2)).
```
If compare code is omitted, the contents of the chain is sorted on alphabetically on their object<-print_name.

If unique equals @on, duplicates (i.e. pairs of objects for which executing the comparison yields equal) will be removed. Default is not to remove duplicates. See also chain->unique.

NOTE: When sorting with a non-function, the result of comparing two element is a boolean and cannot express equal. chain->sort yields an undefined result if the chain contains two or more element for which code->forward and code->forward yield the same result. This undefined behaviour can include a fatal error.

See also
- char_array<-compare
- char_array->smaller
- char_array->larger
- class binary_condition
- vector->sort