Re: Basic debugging checklist

Hi toolic

Nice work, but may I suggest that

> Display the contents of variables using print or warn

> warn "$var\n";

is changed to

warn "<$var>";

Two reasons:

I don't see the point of disabling line and file information from warn by default by appending "\n".
A beginner might get lost where the error originates.
A missing chomp is very common, surrounding brackets <...> helps finding them.
A beginner should be made aware if his variable ends on a newline.

see

C:\>perl
$var = "abc\n";    # trailing newline

warn "$var\n";
warn "<$var>";
warn "$var";

__END__
abc

<abc
> at - line 4.
abc
[download]

Cheers Rolf
_{(addicted to the Perl Programming Language and ☆☆☆☆ :)

Wikisyntax for the Monastery}

update

I just realized that your point 3 covers chomp and detecting whitespace, but I'm still not sure why you're disabling the line info in warn.

Comment on Re: Basic debugging checklist Select or Download Code

Replies are listed 'Best First'.

Re^2: Basic debugging checklist
by Athanasius (Archbishop) on Dec 03, 2017 at 15:08 UTC

On the subject of detecting unexpected whitespace, mention should also be made of another node that regularly appears in Selected Best Nodes:

Unbelievably Obvious Debugging Tip by dreadpiratepeter

Cheers,

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

[reply]

Re^2: Basic debugging checklist
by davies (Prior) on Mar 01, 2020 at 22:14 UTC

I recently got bitten by doing this. The debugging messages were going to the web page. The code was misbehaving, but no debugging messages appeared. View Source explained why - because I had used < and >, they were being interpreted as HTML tags that made no sense & were ignored. Since then, I've been using square brackets.

Regards,

John Davies

[reply]

Re^3: Basic debugging checklist

by LanX (Saint) on Mar 01, 2020 at 23:57 UTC

CGI::Carp

->

-ť

My preference to <...> over [...] stems from the fact that square brackets are easily confused as array syntax by the eye.

I'd suggest to either double or invert the angle brackets, I doubt that <<...>> or >...< are easily confused as HTML tags.

update

I was wrong with the simple doubling, this <<br>> would be a a break surrounded by angles.

Though this might help ->...<-

I'm open for other ASCII suggestions, i.e. avoiding unicode.

Cheers Rolf
_{(addicted to the Perl Programming Language :)

Wikisyntax for the Monastery}

[reply]
[d/l]
[select]

Re^4: Basic debugging checklist

by hippo (Bishop) on Mar 02, 2020 at 09:22 UTC

Mostly I use the apostrophe (ASCII 39 or x27). This helps as I'm used to seeing it delimiting strings so a "missing" terminator at a line end or one with preceding space appears obvious. In those rare occurrences where this is less effective because of the prevalence of apostrophes in the data corpus I sometimes use the tilde instead (ASCII 126 or x7E). HTH.

[reply]

Re^2: Basic debugging checklist
by soonix (Canon) on Dec 03, 2017 at 14:44 UTC

"\n"

print

warn

[reply]
[d/l]
[select]

Re^3: Basic debugging checklist

by QM (Parson) on Dec 05, 2017 at 12:02 UTC

warn

die

warn

print STDERR

-QM
--
Quantum Mechanics: The dreams stuff is made of

[reply]
[d/l]
[select]


P is for Practical
	PerlMonks