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Fix nits in logging section.

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This commit is contained in:
Graydon Hoare 2012-10-05 15:56:45 -07:00
parent 2f50607d88
commit 0dd4b42a00
1 changed files with 11 additions and 16 deletions
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doc/rust.md
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@ -2306,30 +2306,25 @@ logging level:
// Full version, logging a value.
log(core::error, ~"file not found: " + filename);
// Log-level abbreviated, since core::* is imported by default.
// Log-level abbreviated, since core::* is used by default.
log(error, ~"file not found: " + filename);
// Formatting the message using a format-string and #fmt
// Formatting the message using a format-string and fmt!
log(error, fmt!("file not found: %s", filename));
// Using the #error macro, that expands to the previous call.
// Using the error! macro, that expands to the previous call.
error!("file not found: %s", filename);
~~~~
A `log` expression is *not evaluated* when logging at the specified
logging-level, module or task is disabled at runtime. This makes inactive
`log` expressions very cheap; they should be used extensively in Rust
code, as diagnostic aids, as they add little overhead beyond a single
integer-compare and branch at runtime.
A `log` expression is *not evaluated* when logging at the specified logging-level, module or task is disabled at runtime.
This makes inactive `log` expressions very cheap;
they should be used extensively in Rust code, as diagnostic aids,
as they add little overhead beyond a single integer-compare and branch at runtime.
Logging is presently implemented as a language built-in feature, as it makes
use of compiler-provided logic for allocating the associated per-module
logging-control structures visible to the runtime, and lazily evaluating
arguments. In the future, as more of the supporting compiler-provided logic is
moved into libraries, logging is likely to move to a component of the core
library. It is best to use the macro forms of logging (*#error*,
*#debug*, etc.) to minimize disruption to code using the logging facility
when it is changed.
Logging is presently implemented as a language built-in feature,
as it makes use of compiler-provided, per-module data tables and flags.
In the future, logging will move into a library, and will no longer be a core expression type.
It is therefore recommended to use the macro forms of logging (`error!`, `debug!`, etc.) to minimize disruption in code that uses logging.
### Assert expressions