Tcl Source Code

When given only one argument, [dict remove] and [dict replace] seem to return that argument without even looking at it.  Consequently, they can be made to return non-dicts (i.e. invalid list or odd list length) and noncanonical dicts (i.e. with duplicate keys).

When given only one argument, [dict merge] forces the argument to be a dict (thereby rejecting non-lists and odd-length lists), but the string representation is preserved.  Consequently, [dict merge] can be made to return noncanonical dicts.

% dict remove \{\}x
{}x
% dict remove {a 1 b}
a 1 b
% dict remove {a 1 b 2 a 3}
a 1 b 2 a 3
% dict replace \{\}x
{}x
% dict replace {a 1 b}
a 1 b
% dict replace {a 1 b 2 a 3}
a 1 b 2 a 3
% dict merge \{\}x
list element in braces followed by "x" instead of space
% dict merge {a 1 b}
missing value to go with key
% dict merge {a 1 b 2 a 3}
a 1 b 2 a 3
% ::tcl::unsupported::representation [dict merge {a 1 b 2}]
value is a dict with a refcount of 3, object pointer at 0xbeb3b0, internal representation 0xbe11a0:0xbeb860, string representation "a 1 b 2"
% ::tcl::unsupported::representation [dict merge {a 1 b 2 a 3}]
value is a dict with a refcount of 5, object pointer at 0x1c3a560, internal representation 0x1c843a0:0x1c35790, string representation "a 1 b 2 a 3"

Contrast with every other [dict] command that returns a dict and/or sets a dict variable.  They all produce only canonical dicts.

% dict get {a 1 b 2 a 3}
a 3 b 2
% ::tcl::unsupported::representation [dict get {a 1 b 2 a 3}]
value is a list with a refcount of 1, object pointer at 0x99cc90, internal representation 0x9adb00:(nil), no string representation
% ::tcl::unsupported::representation [dict get {a 1 b 2}]
value is a list with a refcount of 1, object pointer at 0x9a09e0, internal representation 0x9db0e0:(nil), no string representation