About the in expression, Why can't use with array.

Ali Çehreli acehreli at yahoo.com
Fri Oct 25 05:17:35 UTC 2019


On 10/24/2019 05:58 AM, lili wrote:
 > Hi:
 >     In Dlang where is strange design. The in expression can only use to
 > associative array, why array can not use in expression.

In addition to the big O surprise, there is another important issue that 
may be seen as either for or against supporting the 'in' operator for 
arrays: With associative arrays, 'in' takes the keys; since keys are 
index values for arrays, the in operator would be trivially


   return (key < __length
           ? &__ptr[key]
           : null);

Given the two differences, 'in' does not make sense on arrays:

- Big O is different

- One wants to use keys for associative arrays but (likely) values for 
arrays

Ali



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