Feature #9049


Shorthands (a:b, *) for inclusive indexing

Added by mohawkjohn (John Woods) about 8 years ago. Updated over 3 years ago.

Target version:


For NMatrix, we've implemented a range shorthand which relies on Hashes: m[1=>3, 2=>4], for example, which returns rows 1 through 3 inclusive of columns 2 through 4 (also inclusive). The original goal was to be able to do m[1:3, 2:4] using the new hash notation, but the new hash notation requires that the key be a symbol — it won't accept an integer.

Whether through the hash interface or not, it'd be lovely if there were a shorthand for slicing matrices (and even Ruby Arrays) using colon. This could just be an alternate syntax for ranges, also — which might make more sense.

The other related shorthand we'd love to find a way to implement is the all-inclusive shorthand. It gets to be a pain to type n[0...n.shape[0], 1...3] to get a submatrix (a slice), and it's really difficult to read. As a work-around, we currently use the :* symbol: n[:*, 1...3]. But it'd be simpler if there were a way to use a splat operator without an operand as a function argument. It might be a special case where the * is treated as a :* automatically. But this edge case might cause confusion with error messages when users make syntax errors elsewhere.

The colon shorthand is the highest priority for us.

Related issues

Related to Ruby master - Feature #14044: Introduce a new attribute `step` in RangeRejectedmatz (Yukihiro Matsumoto)Actions

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