Rename log_err to print

[brson]

log_err is the most common way to get console output, and is usually used in a way that doesn't reflect it's name. For convenience and to make a better impression for 0.1 we should just rename it to 'print'.

[marijnh]

I was about to do this (well, I wanted to use echo) a few weeks back (telling people to use log_err in a tutorial makes it obvious how ridiculous the name is) -- but with the extra debugging cruft that log and log_err output (#1088), it really is a logging statement, not a print.

[brson]

Yeah, I was hoping we could make the logging output prettier too: #1088

[brson]

Regardless of the approach we take, it would be nice for the sake of hello world for printing to be simple. both log_err and io::stdout().write_line(...) are hideous.

We could also create a print() function and put it directly in std, so users could import std::*; print("hello, world").

But seeing as how log is supposed to be so highly integrated into the language, I do kind of think we should be encouraging log. That said, echo might be a better keyword for logging, so we can reserve print for std.

[marijnh]

io::stdout().write_line(...)

I recently added std::io::println and std::io::print, for exactly this reason.

[pcwalton]

print may not be best, since as noted on the mailing list print suggests stdout. echo isn't bad; I was thinking show by analogy with Haskell's Show, since it's polymorphic.

[bstrie]

How about alert, which has analogies to print while avoiding conflation. alert also suggests the more severe level of logging that log_err implies.

[marijnh]

I like alert.

[kud1ing]

I associate "alert" with "Alert dialog box" which is an immediate in-your-face action.
Also JavaScript uses alert() to display a dialog box.

IMHO printing to STDERR is a different form of notification.
I'd be in favor of "print" which is very common in programming languages.

[pcwalton]

+1 for alert.

[brson]

graydon popped up on the mailing list recently to vote for log levels and prelude-defined constants (err, warn, info, debug)

[graydon]

Phew! Finished this today after an embarrassing run of snapshots and partial-rewrites.

The new scheme is this:

log(*level*, *anything*) is a built-in expression form. Level must be a u32 expression, anything can be anything, just like the old log.

log_err is gone

core::debug, core::info, core::warn and core::error are defined in core (thus available everywhere as debug, info, warn and error) and defined as log levels 3, 2, 1, 0 respectively. So you can write log(info, foo) to get info-level logging of foo.

The macros #debug(f, ...), #info(f, ...), #warn(f, ...) and #error(f, ...) are defined in a synthetic chunk of macro-definition buried in the macro expander file (bad place to put it but it works for now, we can factor it out later) and expand to

log(core::debug, #fmt(f, ...))

and similar depending on the macro you use. So you should wind up writing shorter and pithier logging bits using this, since you get #fmt thrown in for free. Just use #debug("foo: %u, bar: %u", f, b) and you get nice output.

There remains some vestigial bad-word support for the words "log_err" and "log_full" in the last snapshots; those will roll over with the next snapshot and vanish but in the meantime the stage1..3 compilers no longer even know about those words.

Hopefully this is ok!

[marijnh]

Awesome! log_err was really starting to become an eyesore.