Change description of underscore-only variables #45964
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Spawned by https://discourse.julialang.org/t/class-of-variables/83892 The rvalue/lvalue description does not seem benefitial. It confuse programmers that are not programming language nerds (it is a cool concept to learn, but this does not seem the place to learn it), and even programming language nerds may object. I for example, find kinda of a stretch to call `___` a lvalue because the linked wikipedia page says: > An l-value refers to an object that persists beyond a single expression. An r-value is a temporary value that does not persist beyond the expression that uses it.[3] Considering this description, the `___` matches more a rvalue than an lvalue (even if it is semantically a location and appear always in the left-hand side of an assignment).
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The error message refers to them as R-values though so as long that is the case, doesn't it make sense to also have that in the documentation? |
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Yes, I forgot to account the error message, but it just says they are not |
Added back a mention to `___` not being `rvalue`s (but nothing about them being `lvalue`s as they do not keep value nor are a real persistent location).
oscardssmith
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Aug 8, 2023
Followup to #45964, #46506, and https://discourse.julialang.org/t/class-of-variables/83892. The error ``` julia> println(_) ERROR: syntax: all-underscore identifier used as rvalue ``` is hard to interpret if you are not familiar with the term `rvalue`, which is not used in any other context in Julia, and as discussed previously the use here is not clearly matching the wikipedia page referred to in the documentation either. This PR does away with the term `rvalue` by changing the error to ``` ERROR: syntax: all-underscore identifiers are write-only and their values cannot be used in expressions ``` and updates the documentation accordingly.
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Spawned by https://discourse.julialang.org/t/class-of-variables/83892
The rvalue/lvalue description does not seem benefitial. It confuse programmers that are not programming language nerds (it is a cool concept to learn, but this does not seem the place to learn it), and even programming language nerds may object. I for example, find kinda of a stretch to call
___a lvalue because the linked wikipedia page says:Considering this description, the
___matches more a rvalue than an lvalue (even if it is semantically a location and appear always in the left-hand side of an assignment).