From Newsgroup: comp.lang.tcl

I don't understand why the error occurs in my script, or where exactly.

missing value to go with key

Why does an error occur in Scenario 4 when I try to use dict set on a
variable initially defined as a list with the same keys and values I
want to add?
Why does no error occur in Scenario 5 when the initial list contains
different keys and values?
The script;

#! /usr/bin/env tclsh

package require dicttool

puts "info patchlevel [info patchlevel]"
puts "tclplatform(os) $tcl_platform(os)"
puts "tclplatform(osVersion) $tcl_platform(osVersion)"

#1.
puts "\n1. without error different variable names dvar1 and dvar2"
set dvar1 [dict create k1 v1 k2 v2]
puts "dvar1: $dvar1 is: [dict is_dict $dvar1]"

dict set dvar2 k3 v3 k4 v4
puts "dvar2: $dvar2 is: [dict is_dict $dvar2]"

#2.
unset dvar1
unset dvar2
puts "\n2. with error same variable name dvar1"
set dvar1 [dict create k1 v1 k2 v2]
puts "dvar1: $dvar1 is: [dict is_dict $dvar1]"

catch {dict set dvar1 k3 v3 k4 v4} err
puts "err: $err"
puts "dvar1: $dvar1 is: [dict is_dict $dvar1]"

#3.
unset dvar1
unset err
puts "\n3. with error same variable name dvar1 but same keys and values
dict create"
set dvar1 [dict create k1 v1 k2 v2]
puts "dvar1: $dvar1 is: [dict is_dict $dvar1]"
puts "length dvar1: [llength $dvar1]"
puts "dvar1: $dvar1 is: [dict is_dict $dvar1]"
set dvar1 [list k1 v1 k2 v2]
puts "dvar1: $dvar1 is: [dict is_dict $dvar1]"
puts "length dvar1: [llength $dvar1]"

catch {dict set dvar1 k3 v3 k4 v4} err
puts "err: $err"
puts "dvar1: $dvar1 is: [dict is_dict $dvar1]"


#4.
unset dvar1
unset err
puts "\n4. with error same variable name dvar1 but same keys and values
dict set"
set dvar1 [dict create k1 v1 k2 v2]
puts "dvar1: $dvar1 is: [dict is_dict $dvar1]"
puts "length dvar1: [llength $dvar1]"
puts "dvar1: $dvar1 is: [dict is_dict $dvar1]"
set dvar1 [list k3 v3 k4 v4]
puts "dvar1: $dvar1 is: [dict is_dict $dvar1]"
puts "length dvar1: [llength $dvar1]"

catch {dict set dvar1 k3 v3 k4 v4} err
puts "err: $err"
puts "dvar1: $dvar1 is: [dict is_dict $dvar1]"

#5.
unset dvar1
unset err
puts "\n5. without error same variable name dvar1 but different keys and values"
set dvar1 [dict create k1 v1 k2 v2]
puts "dvar1: $dvar1 is: [dict is_dict $dvar1]"
puts "length dvar1: [llength $dvar1]"
puts "dvar1: $dvar1 is: [dict is_dict $dvar1]"
set dvar1 [list k5 v5 k6 v6]
puts "dvar1: $dvar1 is: [dict is_dict $dvar1]"
puts "length dvar1: [llength $dvar1]"

catch {dict set dvar1 k3 v3 k4 v4} err
puts "err: $err"
puts "dvar1: $dvar1 is: [dict is_dict $dvar1]"


if {0} {
output:

info patchlevel 8.6.13
tclplatform(os) Linux
tclplatform(osVersion) 6.6.15-amd64

1. without error different variable names dvar1 and dvar2
dvar1: k1 v1 k2 v2 is: 1
dvar2: k3 {v3 {k4 v4}} is: 1

2. with error same variable name dvar1
dvar1: k1 v1 k2 v2 is: 1
err: k1 v1 k2 v2 k3 {v3 {k4 v4}}
dvar1: k1 v1 k2 v2 k3 {v3 {k4 v4}} is: 1

3. with error same variable name dvar1 but same keys and values dict create dvar1: k1 v1 k2 v2 is: 1
length dvar1: 4
dvar1: k1 v1 k2 v2 is: 1
dvar1: k1 v1 k2 v2 is: 1
length dvar1: 4
err: k1 v1 k2 v2 k3 {v3 {k4 v4}}
dvar1: k1 v1 k2 v2 k3 {v3 {k4 v4}} is: 1

4. with error same variable name dvar1 but same keys and values dict set
dvar1: k1 v1 k2 v2 is: 1
length dvar1: 4
dvar1: k1 v1 k2 v2 is: 1
dvar1: k3 v3 k4 v4 is: 1
length dvar1: 4
err: missing value to go with key
dvar1: k3 v3 k4 v4 is: 1

5. without error same variable name dvar1 but different keys and values
dvar1: k1 v1 k2 v2 is: 1
length dvar1: 4
dvar1: k1 v1 k2 v2 is: 1
dvar1: k5 v5 k6 v6 is: 1
length dvar1: 4
err: k5 v5 k6 v6 k3 {v3 {k4 v4}}
dvar1: k5 v5 k6 v6 k3 {v3 {k4 v4}} is: 1

}
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From Newsgroup: comp.lang.tcl

greg <gregor.ebbing@gmx.de> wrote:

I don't understand why the error occurs in my script, or where exactly.

missing value to go with key

Why does an error occur in Scenario 4 when I try to use dict set on a variable initially defined as a list with the same keys and values I
want to add?

#4.
set dvar1 [list k3 v3 k4 v4]

Creates a list of four elements, which when shimmered to a dict will
produce a dict with two keys (k3, k4) each containing one value (v3,
v4) respectively.

dict set dvar1 k3 v3 k4 v4

Attempts to set the chain of keys k3->v3->k4 to the value v4. See the
'dict set' subcommand in the dict manpage, the above is not two keys
with two values but a three level nested dict.

When [dict] looks at dvar1, it finds a k3 key at the top level, it then
looks at the value of k3, finds only "v3" (not a dict) and errors out
because "v3" is not a key.

Why does no error occur in Scenario 5 when the initial list contains different keys and values?

#5.
set dvar1 [list k5 v5 k6 v6]

Creates a list containing four elements, which when shimmered to a
dict, is a dict with two keys (k5, k6) with one value each (v5, v6).

dict set dvar1 k3 v3 k4 v4

Attempts to set the chain of nested keys k3->v3->k4 to the value v4.

When [dict] looks at dvar1, it finds no key "k3", so it creates a new
key "k3", then inside "k3" it creates a new nested dict with a key of
"v3", then inside "v3" it creates a new nested dict with a key of "k4"
and a value of "v4". No error because everything created was all new.


Your test key/value names imply that you think that this:

dict set d1 k1 v1 k2 v2

produces this:

{k1 v1} {k2 v2}

When in fact it produces this:

{k1 {v1 {k2 v2}}}

Those two are two very different dicts. One is a flat dict with two
keys, the other is a three level deep hierarchical dict.

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From Newsgroup: comp.lang.tcl

Am 24.02.24 um 22:26 schrieb Rich:

..
When [dict] looks at dvar1, it finds a k3 key at the top level, it then
looks at the value of k3, finds only "v3" (not a dict) and errors out
because "v3" is not a key.

Ok, now I understand,
thanks
Greg

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