cloudRoutine
commented
7 years ago Posted by Ryan Riley on 1/15/2016 2:17:00 PM
Testing hypothesis that broken windows applies equally to comments ... please share comments or alternatives! Craig Stuntz suggested a few things on Twitter which led me to explain further why I think this operator is a somewhat natural fit: Array slices using a slightly similar operator, ..: [|1;2;3;4|].[1..] = [|2;3;4|] [|1;2;3;4|].[..2] = [|1;2;3|] Suggestion to use [|hd::tl|]: I think :: is restricted to just lists as it is 1) used in the definition of the 'T list type (iirc) and 2) built into the compiler to expect lists (iirc). Suggestion to use [|hd;;tl|]: "error FS0010: Incomplete structured construct at or before this point in pattern” in FSI
Introduce array spread operator for pattern matching and [] [11462964]
Submitted by Ryan Riley on 1/15/2016 12:00:00 AM
[ 18 votes ]
Several languages have introduced a handy spread operator, ..., that can be used to pick up remaining arguments to a function call or when destructuring values. [1] This would be incredibly helpful in F# to reduce boilerplate in methods accepting a [] or when trying to pattern match arrays:
match [|1;2;3;4|] with
| [||] -> // do stuff with empty array
| [|hd;…tl|] -> // do stuff with hd/tl
[1] https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_operator
Response
\ by fslang-admin on 2/3/2016 12:00:00 AM **
Declined per my comment below. We would not extend pattern matching for this one case, but Rick is right that improvements to active patterns may make sense Don Syme, F# Language Evolution