When I use:
puts [format "%s (%s)" ${package} ${blockingPckg}]

I get:
pyppmd (py7zr)

When I use:
lappend manual ${package}
puts ${manual}

I get:
pyppmd

But when I use:
lappend manual [format "%s (%s)" ${package} ${blockingPckg}]
puts ${manual}

I get:
{pyppmd (py7zr)}


What could be happening here? I would expect:
pyppmd (py7zr)

--
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof

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Cecil Westerhof <Cecil@decebal.nl> writes:

When I use:
puts [format "%s (%s)" ${package} ${blockingPckg}]

I get:
pyppmd (py7zr)

When I use:
lappend manual ${package}
puts ${manual}

I get:
pyppmd

But when I use:
lappend manual [format "%s (%s)" ${package} ${blockingPckg}]

It works when I use:
append manual [format "%s (%s) " ${package} ${blockingPckg}]

But I am still interested in what is happening.

puts ${manual}

I get:
{pyppmd (py7zr)}

What could be happening here? I would expect:
pyppmd (py7zr)

--
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof

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On 9/28/22 6:00 PM, Cecil Westerhof wrote:

When I use:
puts [format "%s (%s)" ${package} ${blockingPckg}]

I get:
pyppmd (py7zr)

When I use:
lappend manual ${package}
puts ${manual}

I get:
pyppmd

But when I use:
lappend manual [format "%s (%s)" ${package} ${blockingPckg}]
puts ${manual}

I get:
{pyppmd (py7zr)}

What could be happening here? I would expect:
pyppmd (py7zr)

It is because of the space: Your manual variable is a list, which
contains an element with characters that require special handling in
Tcl, which here happens to be the space character. Space is also the
default delimiter that [puts] uses when printing lists. In this case,
it would cause a confusion as to whether what it printed was two
separate elements, or a single element with spaces in it.

Try eliminating the space by using "%s(%s)" as the format or try using
[join $manual] before printing it.

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Try these:

puts [list "a c"]

should show: {a c}

and

puts [list "abc"]

should show: abc

In both cases puts displays the string representation of a list
with a single entry which is a 3 character string.
The {a c} is braced so the string "a c" will be parsed as a single list entry
if string is interpreted as a list.

Dave B

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On 9/28/22 6:42 PM, Cecil Westerhof wrote:

But when I use:
lappend manual [format "%s (%s)" ${package} ${blockingPckg}]

It works when I use:
append manual [format "%s (%s) " ${package} ${blockingPckg}]

But I am still interested in what is happening.

[lappend] and [append] are two very different commands, operating on
lists vs. strings. Hopefully my previous message explained the why here.

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Cecil Westerhof <Cecil@decebal.nl> wrote:

But when I use:
lappend manual [format "%s (%s)" ${package} ${blockingPckg}]
puts ${manual}

I get:
{pyppmd (py7zr)}

What could be happening here? I would expect:
pyppmd (py7zr)

Not from Tcl you shouldn't.

When you "puts" a list, Tcl outputs a string encoded such that it can
be converted back into the same list structure again later.

The { and } appear because space is normally a list element separator,
but when the separator appears in the value of an element, it is
'escaped' by surrounding the value with { }.

It is the same reasoning as to why CSV elements, themselves containing
commas as data, get surrounded by double quote characters.


Note this part of the 'list' manpage description:

Braces and backslashes get added as necessary, so that the
lindex command may be used on the result to re-extract the
original arguments, ...

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Am 29.09.2022 um 00:00 schrieb Cecil Westerhof:

When I use:
puts [format "%s (%s)" ${package} ${blockingPckg}]

I get:
pyppmd (py7zr)

When I use:
lappend manual ${package}
puts ${manual}

I get:
pyppmd

But when I use:
lappend manual [format "%s (%s)" ${package} ${blockingPckg}]
puts ${manual}

I get:
{pyppmd (py7zr)}

lappend is a list append and transforms each parameter to a valid list
element. As the string contains a space, curly braces aree added.
To make it simpler, you may write:
lappend manual "pyppmd (py7zr)"

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Harald Oehlmann <wortkarg3@yahoo.com> writes:

Am 29.09.2022 um 00:00 schrieb Cecil Westerhof:

When I use:
puts [format "%s (%s)" ${package} ${blockingPckg}]
I get:
pyppmd (py7zr)
When I use:
lappend manual ${package}
puts ${manual}
I get:
pyppmd
But when I use:
lappend manual [format "%s (%s)" ${package} ${blockingPckg}]
puts ${manual}
I get:
{pyppmd (py7zr)}

lappend is a list append and transforms each parameter to a valid list element. As the string contains a space, curly braces aree added.
To make it simpler, you may write:
lappend manual "pyppmd (py7zr)"

I do not think that that will work, because the format is giving that
string.

--
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof

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saitology9 <saitology9@gmail.com> writes:

On 9/28/22 6:00 PM, Cecil Westerhof wrote:

When I use:
puts [format "%s (%s)" ${package} ${blockingPckg}]
I get:
pyppmd (py7zr)
When I use:
lappend manual ${package}
puts ${manual}
I get:
pyppmd
But when I use:
lappend manual [format "%s (%s)" ${package} ${blockingPckg}]
puts ${manual}
I get:
{pyppmd (py7zr)}

What could be happening here? I would expect:
pyppmd (py7zr)

It is because of the space: Your manual variable is a list, which
contains an element with characters that require special handling in
Tcl, which here happens to be the space character. Space is also the
default delimiter that [puts] uses when printing lists. In this case,
it would cause a confusion as to whether what it printed was two
separate elements, or a single element with spaces in it.

Try eliminating the space by using "%s(%s)" as the format or try using
[join $manual] before printing it.

I use tclsh not enough. I should have know this. :'-(

First I only saved the package name, now I add the blocking package. I
should have used append instead of lappend from day one, but in the
original case the result was the same. So it did not have
consequences.
But it was still a bug in my opinion: I needed a string, so no reason
to work with a list.


By the way I use a tclsh script to keep my python pip up to date. :-D

--
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof

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Cecil Westerhof <Cecil@decebal.nl> writes:

append manual [format "%s (%s) " ${package} ${blockingPckg}]

And I make thing needlessly difficult again. I should just use:
append manual "${package} (${blockingPackage}) "

--
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof

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Cecil Westerhof <Cecil@decebal.nl> wrote:

Harald Oehlmann <wortkarg3@yahoo.com> writes:

Am 29.09.2022 um 00:00 schrieb Cecil Westerhof:

When I use:
puts [format "%s (%s)" ${package} ${blockingPckg}]
I get:
pyppmd (py7zr)
When I use:
lappend manual ${package}
puts ${manual}
I get:
pyppmd
But when I use:
lappend manual [format "%s (%s)" ${package} ${blockingPckg}]
puts ${manual}
I get:
{pyppmd (py7zr)}

lappend is a list append and transforms each parameter to a valid list
element. As the string contains a space, curly braces aree added.
To make it simpler, you may write:
lappend manual "pyppmd (py7zr)"

I do not think that that will work, because the format is giving that
string.

Harald's version will produce the same output as your format:

$ rlwrap tclsh
% lappend manual "pyppmd (py7zr)"
{pyppmd (py7zr)}
% puts $manual
{pyppmd (py7zr)}
%

You get the curly braces because of the space inside element zero, not
because you used format to generate the string that became element
zero's content.

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Cecil Westerhof <Cecil@decebal.nl> wrote:

I use tclsh not enough. I should have know this. :'-(

First I only saved the package name, now I add the blocking package.
I should have used append instead of lappend from day one, but in the original case the result was the same. So it did not have
consequences.

But it was still a bug in my opinion: I needed a string, so no reason
to work with a list.

Yes, and it is a "latent, hiding, data dependent bug". Using 'lists'
when you really want a plain string can most often seem to work fine,
because the basic, unescaped, string rep often looks identical to just
a plain string.

Then, months or years later, your code consumes a data value containing
a list 'meta-character' and the list escaping code does what you asked,
and escapes the string representation of the list values, and you have
either weird data being produced, or you have an actual exception error situation.

It is in general best to never use list operators on plain strings, and
to never use string operators on lists. It is possible to do so
safely, but doing so is an 'advanced technique' and the programmer has
to fully understand the ramifications of what they are asking the
runtime to perform.

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Cecil Westerhof <Cecil@decebal.nl> wrote:

Cecil Westerhof <Cecil@decebal.nl> writes:

append manual [format "%s (%s) " ${package} ${blockingPckg}]

And I make thing needlessly difficult again. I should just use:
append manual "${package} (${blockingPackage}) "

For plain strings, yes.

If you /want/ formatting (i.e. fixed width columns, or real's to a
specific decimal place, etc.) then of course use format.

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