Course of Raku / Objects, I/O, and exceptions / Input and output / Standard streams / Exercises / Note a warning

Solution: Note a warning

Here is a possible solution to the task.

Code

my $value = -3;

note 'Warning: the value is negative' if $value < 0;
say $value.abs;

🦋 You can find the source code in the file note-a-warning.raku.

Output

Warning: the value is negative
3

Comments

note sends the warning to standard error, and only when the value is actually negative. say sends the real result — the absolute value 3 — to standard output.
Keeping the diagnostic on standard error means it does not pollute the program’s real output: discarding standard error with 2>/dev/null leaves just the 3 behind.

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