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Comment by kibwen | Hacker News Reader

Not sure why this is being downvoted. The GP commenter is mistaken, the following line is completely valid Rust:

    const USAGE: &str = "usage: blah blah";

Compare it to the equivalent in C:

    const char *USAGE = "usage: blah blah";

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And while you are at it, compare that to:

  #define USAGE "usage: blah blah"

The equivalent C needs a second const -- your first one refers to the data behind the string but not the string pointer, and is more like Rust's `let usage: &str`.

    const char * const USAGE = "usage: blah blah";

Or rather `let mut usage: &str`. Rust actually is kind of similar to C here in that the pointer and pointee can be separately const or mutable. But in Rust "const" is the default and mut needing to be explicitly declared, whereas with C it's the other way around.

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