Provided by: tcllib_1.15-dfsg-2_all 
NAME
tepam::procedure - TEPAM procedure, reference manual
SYNOPSIS
package require Tcl 8.3
package require tepam ?0.4?
tepam::procedure name attributes body
_________________________________________________________________
DESCRIPTION
This package provides an alternative way to declare Tcl procedures and to manage its arguments. There is
a lot of benefit to declare a procedure with TEPAM rather than with the Tcl standard command proc: TEPAM
allows specifying inside the procedure declaration all information that is required to generate
comprehensive documentations and help support. The information is also used by an automatically invoked
argument checker that validates the provided procedure arguments before the procedure body is executed.
Finally, a procedure can be called interactively which will open a graphical form that allows specifying
the procedure arguments.
TEPAM simplifies also the handling of the different types of argument, like the named arguments (often
also called options) and the unnamed arguments. TEPAM supports the named first, unnamed later style
(typical Tcl command style) as well as also the unnamed first, named later style (typical Tk command
style). TEPAM takes care about default values for arguments, optional arguments, multiple applicable
arguments, etc. and eliminates the need to check the validity of the argument inside the procedure
bodies.
An informal overview of all the TEPAM procedure declaration and calling features as well as a short
introduction into TEPAM is provided by tepam(3tcl).
TERMINOLOGY
The exact meaning of several terms that are used in this document will be shortly explained to avoid any
ambiguities and misunderstandings.
Subcommand
The usage of subcommands is heavily used in the Tcl language. Several commands are incorporated
into a single main command and are selectable via the first argument.
The string command is an example of such a command that implements for example subcommands to
check a character string's length, to compare strings, to extract substrings, etc:
string length string
string compare string string
string range string first last
TEPAM provides a framework that allows implementing easily such subcommands in form of Tcl procedures. It
allows not only defining a first level of subcommands, but also a higher level of subcommands. The string
command's class check could be implemented as independent sub-sub-commands of the string command:
string is alnum string
string is integer string
string is double string
Procedure attribute
TEPAM allows attaching to a declared procedure different kind of attributes. Some of these
attributes are just used for documentation purposes, but other attributes specify the way how the
procedure has to be called. Also the procedure arguments are defined in form of a procedure
attribute.
Argument
TEPAM uses the term argument for the parameters of a procedure.
The following example calls the subcommand string compare with several arguments:
string compare -nocase -length 3 "emphasized" "emphasised"
The following paragraphs discuss these different argument types.
Named argument
Some parameters, as -length 3 of the subcommand string compare have to be provided as pairs of
argument names and argument values. This parameter type is often also called option.
TEPAM uses the term named argument for such options as well as for the flags (see next item).
Flag, switch
Another parameter type is the flag or the switch. Flags are provided simply by naming the flag
leading with the '-' character. The -nocase of the previous string compare example is such a flag.
Flags are considered by TEPAM like a special form of named arguments.
Unnamed argument
For the other parameters, e.g. the ones for which the argument name has not to be mentioned, TEPAM
uses the term unnamed argument. The previous string compare example uses for the two provided
character strings two unnamed arguments.
Argument attribute
TEPAM allows describing the purpose of each procedure argument with argument attributes. While
some of them are just documenting the attributes, most attributes are used by an argument manager
to control and validate the arguments that are provided during a procedure call. Argument
attributes are used to specify default values, parameter classes (integer, xdigit, font, ...),
choice validation lists, value ranges, etc.
Named arguments first, unnamed arguments later
The string compare command of the previous example requires that the named arguments (options,
flags) are provided first. The two mandatory (unnamed) arguments have to be provided as last
argument.
This is the usual Tcl style (exceptions exist) which is referred in the TEPAM documentation as
named arguments first, unnamed arguments later style.
Unnamed arguments first, named arguments later
In contrast to most Tcl commands, Tk uses generally (exceptions exist also here) a different
calling style where the unnamed arguments have to be provided first, before the named arguments
have to be provided:
pack .ent1 .ent2 -fill x -expand yes -side left
This style is referred in the TEPAM documentation as unnamed arguments first, named arguments
later style.
PROCEDURE DECLARATION
TEPAM allows declaring new Tcl procedures with the command tepam::procedure that has similar to the
standard Tcl command proc also 3 arguments:
tepam::procedure name attributes body
The TEPAM procedure declaration syntax is demonstrated by the following example:
tepam::procedure {display message} {
-short_description
"Displays a simple message box"
-description
"This procedure allows displaying a configurable\
message box. The default message type that is\
created is a warning, but also errors and info can\
be generated.
The procedure accepts multiple text lines."
-example
{display message -mtype Warning "Save first your job"}
-args {
{-mtype -choices {Info Warning Error} \
-default Warning -description "Message type"}
{text -type string -multiple \
-description "Multiple text lines to display"}
}
} {
puts "Message type: $mtype"
puts "Message: $text"
}
The 3 arguments of procedure are:
name The procedure name can be used in very flexible ways. Procedure names can have namespace
qualifiers. By providing a two element name list as procedure name, a subcommand of a procedure
will be declared. It is even possible to declare sub-sub-commands of a procedure by providing name
lists with three elements.
Here are some valid procedure declarations using different procedure names (the attribute and body
arguments are empty for simplicity):
# Simple procedure name:
tepam::procedure display_message {} {}
# Procedure declared in the main namespace:
tepam::procedure ::display_message {} {}
# Procedure in the namespace ::ns:
tepam::procedure ::ns::display_message {} {}
# Declaration of the subcommand message of the procedure display:
tepam::procedure {display message} {} {}
attributes
All procedure attributes are provided in form of an option list that contains pairs of option
names and option values. The example above has as procedure attribute a short and a normal
description, but also the procedure arguments are defined in form of a procedure attribute.
Most procedure attributes are providing information for documentation purposes. But some of them
affect also the way how the procedure can be called. The section Procedure Attributes discusses in
detail the available procedure attributes.
The procedure arguments are defined in form of a special procedure attribute. Most of the
information provided in the argument definition is not just used for documentation purposes. This
information is in fact used by the TEPAM argument manager to handle and validate the various forms
of arguments that are provided during the procedure calls. The section Argument Declaration
discusses in detail all the argument definition attributes.
body This is the normal procedure body. The declared arguments will be available to the procedure body
in form of variables.
The procedure body will only be executed if the provided set of arguments could be validated by
the TEPAM argument manager.
tepam::procedure {display_message} {
-args {
{-mtype -default Warning -choices {Warning Error}}
{text -type string}
}
} {
puts "Message type: $mtype"
puts "Message: $text"
}
The commands procedure as well as argument_dialogbox are exported from the namespace tepam. To use these
commands without the tepam:: namespace prefix, it is sufficient to import them into the main namespace:
namespace import tepam::*
procedure {display_message} {
-args {
PROCEDURE ATTRIBUTES
The first group of procedure attributes is not affecting the behavior of the declared procedure. These
attributes are just used for the purpose of documentation and help text generation:
-category string
A category can be assigned to a procedure for documentation purposes. Any string is accepted as
category.
-short_description string
The short description of a procedure is used in the documentation summary of a generated procedure
list as well as in the NAME section of a generated procedure manual page.
-description string
The (full) description assigned to a procedure is used to create user manual and help pages.
-return string
The -return attribute allows defining the expected return value of a procedure (used for
documentation purposes).
-example string
A help text or manual page of a procedure can be enriched with eventual examples, using the
-example attribute.
The following attributes are not relevant for the documentation and help text generation, but they affect
the behavior of the declared procedure:
-named_arguments_first 0|1
This attribute defines the calling style of a procedure. TEPAM uses by default the named arguments
first, unnamed arguments later style (Tcl). This default behavior can globally be changed by
setting the variable tepam::named_arguments_first to 0. This global calling style can be changed
individually for a procedure with the procedure's -named_arguments_first attribute.
-auto_argument_name_completion 0|1
The declared procedures will by default automatically try to match eventually abbreviated argument
names to the defined arguments names. This default behavior can globally be changed by setting the
variable tepam::auto_argument_name_completion to 0. This global setting of the automatic argument
name completion can be changed individually for a procedure with the
-auto_argument_name_completion procedure attribute.
-interactive_display_format extended|short
A procedure declared with the TEPAM procedure command can always be called with the -interactive
option. By doing so, a graphical form will be generated that allows specifying all procedure
argument values. There are two display modes for these interactive forms. While the extended mode
is more adapted for small procedure argument sets, the short form is more adequate for huge
procedure argument sets.
The choice to use short or extended forms can be globally configured via the variable
tepam::interactive_display_format. This global setting can then be changed individually for a
procedure with the -interactive_display_format procedure attribute.
-args list
The procedure's arguments are declared via the -args attribute. An argument is defined via a list
having as first element the argument name, followed by eventual argument attributes. All these
argument definition lists are packaged themselves into a global list that is assigned to the
procedure's -args attribute.
The argument definition syntax will be described more in detail in the following sub section.
The following attribute allows controlling the logging settings for an individual procedure:
-command_log 0|1|"interactive"
This argument configures the logging of the procedure calls into the list variable
tepam::ProcedureCallLogList. The default configuration defined by the variable tepam::command_log
will be used if this argument is not defined in a procedure declaration.
Setting this argument to 0 will disable any procedure call loggings, setting it to 1 will log any
procedure calls and setting it to interactive will log just the procedures that are called
interactively (procedures called with the -interactive flag).
ARGUMENT DECLARATION
The following example shows the structure that is used for the argument definitions in the context of a
procedure declaration:
tepam::procedure {display_message} {
-args {
{-mtype -default Warning -choices {Info Warning Error} -description "Message type"}
{-font -type font -default {Arial 10 italic} -description "Message text font"}
{-level -type integer -optional -range {1 10} -description "Message level"}
{-fg -type color -optional -description "Message color"}
{-log_file -type file -optional -description "Optional message log file"}
{text -type string -multiple -description "Multiple text lines to display"}
}
} {
}
Each of the procedure arguments is declared with a list that has as first element the argument name,
followed by eventual attributes. The argument definition syntax can be formalized in the following way:
tepam::procedure <name> {
-args {
{<argument_name_1> <arg_attr_name_1a> <arg_attr_value_1a> \
<arg_attr_name_1b> <arg_attr_value_1b> ...}
{<argument_name_2> <arg_attr_name_2a> <arg_attr_value_2a> \
<arg_attr_name_2b> <arg_attr_value_2b> ...}
}
} <body>
The argument names and attributes have to be used in the following way:
Argument name (<argument_name_<n>>)
The provided argument name specifies whether the argument is an unnamed argument or a named
argument. In addition to this, an argument name can also be blank to indicate an argument comment,
or it can start with # to indicate a section comment.
"<Name>"
This is the simplest form of an argument name: An argument whose name is not starting with
'-' is an unnamed argument. The parameter provided during a procedure call will be assigned
to a variable with the name <Name>.
tepam::procedure {print_string} {
-args {
{text -type string -description "This is an unnamed argument"}
}
} {
puts $text
}
print_string "Hello"
-> Hello
"-<Name>"
An argument whose name starts with '-' is a named argument (also called option). The
parameter provided during a procedure call will be assigned to a variable with the name
<Name> (not -<Name>).
tepam::procedure {print_string} {
-args {
{-text -type string -description "This is a named argument"}
}
} {
puts $text
}
print_string -text "Hello"
-> Hello
"--" This flag allows clearly specifying the end of the named arguments and the beginning of the
unnamed arguments, in case the named arguments first, unnamed arguments later style (Tcl)
has been selected.
If the unnamed arguments first, named arguments later style (Tk) style is selected, this
flag is ignored if the unnamed arguments have already been parsed. Otherwise it will be
assigned to the corresponding unnamed argument.
"-" or ""
A blank argument name (either '-' or '') starts a comment for the following arguments.
tepam::procedure {print_time} {
-interactive_display_format short
-args {
{hours -type integer -description "Hour"}
{minutes -type integer -description "Minute"}
{- The following arguments are optional:}
{seconds -type integer -default 0 -description "Seconds"}
{milliseconds -type integer -default 0 -description "Milliseconds"}
}
} {
puts "${hour}h${minutes}:[expr $seconds+0.001*$milliseconds]"
}
Argument comments are basically used in the graphical argument definition forms that are
created if a procedure is called interactively.
"#*" An argument definition list that starts with '#' is considered as a section comment. The
argument definition list will be trimmed from the '#' characters and the remaining string
will be used as section comment.
Section comments can be used to structure visually the argument definition code. Section
comments are also used to structure the generated help texts and the interactive argument
definition forms.
tepam::procedure {complex_multiply} {
-description "This function perform a complex multiplication"
-args {
{#### First complex number ####}
{-r0 -type double -description "First number's real part"}
{-i0 -type double -description "First number's imaginary part"}
{#### Second complex number ####}
{-r1 -type double -description "Second number's real part"}
{-i1 -type double -description "Second number's imaginary part"}
}
} {
return [expr $r0*$r1 - $i0*$i1]
}
Argument attributes (<arg_attr_name_<mn>> <arg_attr_value_<mn>>)
The following argument attributes are supported:
-description string
The description argument attribute is used for documentation purpose. Interactive argument
definition forms use this attribute to provide explanations for an argument.
-type type
The type argument attribute allows assigning the argument either to a predefined data type,
or to an application specific data type. The argument values that are provided during a
procedure call are automatically checked with respect to the defined argument type.
The section ARGUMENT TYPES provides a list of predefined data types and explains how
application specific types can be specified.
The argument type none has a special meaning. An argument that has the type none is handled
as a flag. A flag is always optional and its related variable contains the logical value 1
if the flag has been defined during the procedure call, or otherwise 0.
-default value
Eventual default values can be defined with the -default argument attribute. Arguments with
default values are automatically optional arguments.
-optional|-mandatory
Arguments are by default mandatory, unless a default value is defined. The flag -optional
transforms an argument into an optional argument.
In case an optional argument is not defined during a procedure call, the corresponding
variable will not be defined. The flag -mandatory is the opposite to -optional. This flag
exists only for completion reason, since an argument is anyway mandatory by default.
-multiple
Arguments that have the -multiple attribute can be defined multiple times during a
procedure call. The values that are provided during a procedure call for such an argument
are stored in a list variable. This is even the case if such an argument is only defined
once during a procedure call.
The -multiple attribute can be attributed to unnamed arguments and to named arguments. The
pair of argument name/argument value has to be repeated for each provided value in case of
a named argument. In case the argument with the -multiple attribute is an unnamed
argument, this one has to be the absolute last one of all unnamed arguments.
-choices list
A possible set of valid argument values can be attributed to an argument via the -choices
attribute. The argument value provided during a procedure call will be checked against the
provided choice values.
-choicelabels list
An eventual short description can be attributed to each choice option with the
-choicelabels attribute. These descriptions will be used in the generated help texts and as
radio and check box labels for the interactive calls.
The -choicelabels attribute is optional, but if it is defined, its list needs to have the
identical size as the -choices argument list.
-range {double double}
Another argument constraint can be defined with the -range attribute. The valid range is
defined with a list containing the minimum valid value and a maximum valid value. The
-range attribute has to be used only for numerical arguments, like integers and doubles.
-validatecommand script
Eventual more complex argument value validations can be performed via specific validation
commands that are assigned to the -validatecommand attribute. The provided validation
command can be a complete script in which the pattern %P is replaced by the argument value
that has to be validated. An example of a validation command declaration is:
tepam::procedure {display_message} {
-args {
{text -type string -description "Message text" \
-validatecommand "IllegalWordDetector %P"}
} {
}
-widget string
The widgets that allow defining the different arguments in case of an interactive procedure
call are normally selected automatically in function of the argument type. The -widget
attribute allows specifying explicitly a certain widget type for an argument.
-auxargs list
In case a procedure is called interactively, additional argument attributes can be provided
to the interactive argument definition form via the -auxargs attribute that is itself a
list of attribute name/attribute value pairs:
-auxargs {-<arg_attr_name_1a> <arg_attr_value_1a> \
-<arg_attr_name_1b> <arg_attr_value_1b>
}
For example, if a procedure takes as argument a file name it may be beneficial to specify
the required file type for the interactive argument definition form. This information can
be provided via the -auxargs attribute to the argument definition form:
tepam::procedure LoadPicture {
-args {
{FileName -type existingfile -description "Picture file" \
-auxargs {-filetypes {{"GIF" {*.gif}} {"JPG" {*.jpg}} }}}
}
} {
}
-auxargs_commands script
If the auxiliary argument attributes are not static but have to be dynamically adaptable,
the -auxargs_commands allows defining them via commands that are executed during a
procedure call. A list of pairs of auxiliary attribute names and commands has to be
provided to the -auxargs_commands attribute. The provided commands are executed in the
context of the calling procedure.
-auxargs_commands {-<arg_attr_name_1a> <arg_attr_command_1a> \
-<arg_attr_name_1b> <arg_attr_command_1b>
}
VARIABLES
Several variables defined inside the ::tepam namespace are impacting the mode of operation of the
procedures that have been declared with TEPAM' procedure command.
named_arguments_first
This variable defines the general calling style of the procedures. It is by default set to 1 which
selects the named arguments first, unnamed arguments later style (Tcl style).
By setting this variable to 0, the named arguments first, unnamed arguments later style is
globally selected (Tk style):
set tepam::named_arguments_first 0
While this variable defines the general calling style, the procedure attribute -named_arguments_first can
adapt this style individually for each declared procedure.
auto_argument_name_completion
This variable controls the general automatic argument name matching mode. By default it is set to
1, meaning that the called procedures are trying to match eventually abbreviated argument names
with the declared argument names.
By setting this variable to 0 the automatic argument name matching mode is disabled:
set tepam::auto_argument_name_completion 0
While this variable defines the general matching mode, the procedure attribute
-auto_argument_name_completion can adapt this mode individually for each declared procedure.
interactive_display_format
A procedure declared via the TEPAM procedure command can always be called with the -interactive
switch. By doing so, a graphical form will be generated that allows entering interactively all
procedure arguments.
There are two display modes for these interactive forms. The extended mode which is the default
mode is more adapted for small procedure argument sets. The short form is more adequate for huge
procedure argument sets:
set tepam::interactive_display_format "short"
The choice to use short or extended forms can be globally configured via the variable
interactive_display_format. This global setting can be changed individually for a procedure with the
procedure attribute -interactive_display_format.
help_line_length
The maximum line length used by the procedure help text generator can be specified with this
variable. The default length which is set to 80 (characters) can easily be adapted to the need of
an application:
set tepam::help_line_length 120
Since this variable is applied directly during the help text generation, its value can
continuously be adapted to the current need.
command_log
Procedure calls can be logged inside the list variable tepam::ProcedureCallLogList. The variable
tepam::command_log controls the default logging settings for any procedures. The following
configurations are supported:
• 0: Disables any procedure call loggings
• 1: Enables any procedure call loggings
• "interactive": Will log any procedures called interactively (e.g. procedures called with
the -interactive flag). This is the default configuration.
This default logging configuration can be changed individually for each procedure with the
-command_log attribute.
ARGUMENT TYPES
A comprehensive set of procedure argument types that is already predefined by TEPAM can easily be
completed with additional types that are required for a specific application.
PREDEFINED ARGUMENT TYPES
To remember, a type can be assigned to each specified procedure argument:
tepam::procedure {warning} {
-args {
{-font -type font -default {Arial 10 italic}}
{-severity_level -type integer -optional -range {1 10}}
{-fg -type color -optional -description "Message color"}
{text -type string -multiple -description "Multiple text lines to display"}
}
} {
}
There are some special purpose types that are building the first category of predefined argument types:
• none
A flag, also called switch, is defined as a named argument that has the type none. Flags are
always optional and the default value of the assigned variable is set to 0. In contrast to the
(normal) named arguments, no argument value has to be provided to a flag.
tepam::procedure flag_test {
-args {
{-flag -type none -description "This is a flag"}
}
} {
puts $flag
}
flag_test
-> 0
flag_test -flag
-> 1
Since no argument value has to be provided to a flag, also no data check is performed for this argument
type.
• string
String is a generic argument data type. Any data string can be provided to a string type argument
and no data type checks are therefore performed. The string type allows defining single line
strings during the interactive procedure calls.
• text
Text is identical to string with the exception that it allows entering multi line strings during
interactive procedure calls.
• {}
A blank argument type signifies an undefined argument type. This is the default argument type that
will be used if no type has been explicitly specified. An argument that has a blank type behaves
identically than an argument that has a string type, e.g. no argument data checks are performed.
The only difference is that the data type string is mentioned in the generated help documentation,
while this is not the case for blank type.
Several numerical types are defined by TEPAM. The type validation procedures are using the string is
<type> -strict commands to check the validity of the provided arguments, which assures that no empty
strings are accepted as argument value. The type validation expression for the numerical types and the
argument types to which this expression is applied are:
string is <type_to_check> -strict <argument_value>
• boolean
• integer
• double
Empty strings are accepted as argument value for all the alpha numeric argument types. The argument types
that are falling into this category and validation expression used for them are:
string is <type_to_check> <argument_value>
• alnum
• alpha
• ascii
• control
• digit
• graph
• lower
• print
• punct
• space
• upper
• wordchar
• xdigit
In addition to the data types checked with the string is <type> commands, TEPAM specifies some other
useful data types:
• char
Each string that has a length of 1 character meets the character type. The type check is made with
the following expression:
expr [string length <argument_value>]==1
• color
Any character strings that are accepted by Tk as a color are considered as valid color argument.
Please note that the Tk package has to be loaded to use the type color. TEPAM is using the
following command to validate the color type:
expr ![catch {winfo rgb . <argument_value>}]
• font
Any character strings that are accepted by Tk as a font are considered as valid font argument.
Please note that the Tk package has to be loaded to use the font type. TEPAM is using the
following command to validate the color type:
expr ![catch {font measure <argument_value> ""}]
• file
Any strings that are not containing one of the following characters are considered as valid file
names: * ? " < >. It is not necessary that the file and its containing directory exist. Zero-
length strings are not considered as valid file names.
The following expression is used to validate the file names:
expr [string length <argument_value>]>0 && ![regexp {[\"*?<>:]} <argument_value>]
• existingfile
The argument is valid if it matches with an existing file. The following check is performed to
validate the arguments of this type:
file exists <argument_value>
• directory
The directory argument is validated exactly in the same way as the file arguments.
• existingdirectory
The argument is valid if it matches with an existing directory. The following check is performed
to validate the arguments of this type:
file isdirectory <argument_value>
DEFINING APPLICATION SPECIFIC ARGUMENT TYPES
To add support for a new application specific argument type it is just necessary to add into the
namespace tepam a validation function Validation(<type>). This function requires one argument. It has to
returns 1 if the provided argument matches with the relevant data type. The function has to return
otherwise 0.
The validation command section of the "tepam.tcl" package provides sufficient examples of validation
functions, since it implements the ones for the standard TEPAM types.
The following additional code snippet shows the validation function for a custom argument type that
requires values that have a character string length of exactly 2:
proc tepam::Validate(two_char) {v} {expr [string length $v]==2}
PROCEDURE CALLS
HELP
Each procedure can be called with the -help flag. The procedure will then print a generated help text to
stdout and will then return without performing any additional actions.
Taking the first procedure declared in PROCEDURE CALLS, the help request and the printed help text would
be:
display message -help
->
NAME
display message - Displays a simple message box
SYNOPSIS
display message
[-mtype <mtype>]
Message type, default: "Warning", choices: {Info, Warning, Error}
<text>
Multiple text lines to display, type: string
DESCRIPTION
This procedure allows displaying a configurable message box. The default
message type that is created is a warning, but also errors and info can
be generated.
The procedure accepts multiple text lines.
EXAMPLE
display message -mtype Warning "Save first your job"
The argument manager is checking if the last provided argument is -help and generates the requested help
message if this is the case. So, also the following example will print the help message:
display message -mtype Info "It is 7:00" -help
On the other hand, the following call will result in an error:
display message -help -mtype Info "It is 7:00"
->
display message: Argument '-help' not known
INTERACTIVE PROCEDURE CALL
Calling a procedure with the -interactive flag will open a graphical form that allows specifying
interactively all procedure arguments. The Tk library has to be loaded to use the interactive call. The
following example assures that the Tk library is loaded and shows the command line to call interactively
the procedure declared in PROCEDURE CALLS:
package require Tk
display message -interactive
Also the -interactive flag has to be placed at the last argument position as this is also required for
the -help flag. Arguments defined before the -interactive flag will be ignored. The following example is
therefore also a valid interactive procedure call:
display message -mtype Info "It is 7:00" -interactive
UNNAMED ARGUMENTS
Unnamed arguments are typically provided to the called procedure as simple parameters. This procedure
calling form requires that the provided arguments are strictly following the order of the specified
arguments. Several parameters can be assigned to the last argument if this one has the -multiple
attribute. So, the following declared procedure ...
tepam::procedure {display_message} {
-args {
{mtype -choices {Info Warning Error}}
{text -type string -multiple}
}
} {
puts "$mtype: [join $text]"
}
display_message Info "It is PM 7:00."
-> Info: It is PM 7:00.
display_message Info "It is PM 7:00." "You should go home."
-> Info: It is PM 7:00. You should go home.
The nice thing is that unnamed arguments can also be called as named arguments, which can be handy, for
example if the exact specified argument order is not known to a user:
display_message -mtype Info -text "It is PM 7:00."
-> Info: It is PM 7:00.
display_message -text "It is PM 7:00." -mtype Info
-> Info: It is PM 7:00.
display_message -mtype Info -text "It is PM 7:00." -text "You should go home."
-> Info: It is PM 7:00. You should go home.
display_message -text "It is PM 7:00." -text "You should go home." -mtype Info
-> Info: It is PM 7:00. You should go home.
NAMED ARGUMENTS
Named arguments have to be provided to a procedure in form of a parameter pairs composed by the argument
names and the argument values. The order how they are provided during a procedure call is irrelevant and
has not to match with the argument specification order.
The following declared procedure ...
tepam::procedure {display_message} {
-args {
{-mtype -choices {Info Warning Error}}
{-text -type string -multiple}
}
} {
puts "$mtype: [join $text]"
}
display_message -mtype Info -text "It is PM 7:00."
-> Info: It is PM 7:00.
display_message -text "It is PM 7:00." -mtype Info
-> Info: It is PM 7:00.
display_message -mtype Info -text "It is PM 7:00." -text "You should go home."
-> Info: It is PM 7:00. You should go home.
display_message -text "It is PM 7:00." -text "You should go home." -mtype Info
-> Info: It is PM 7:00. You should go home.
Also named arguments that have not the -multiple attribute can be provided multiple times. Only the last
provided argument will be retained in such a case:
display_message -mtype Info -text "It is PM 7:00." -mtype Warning
-> Warning: It is PM 7:00.
UNNAMED ARGUMENTS FIRST, NAMED ARGUMENTS LATER (TK STYLE)
A procedure that has been defined while the variable tepam::named_arguments_first was set to 1, or with
the procedure attribute -named_arguments_first set to 1 has to be called in the Tcl style. The following
procedure declaration will be used in this section to illustrate the meaning of this calling style:
set tepam::named_arguments_first 1
tepam::procedure my_proc {
-args {
{-n1 -default ""}
{-n2 -default ""}
{u1 -default ""}
{u2 -default ""}
}
} {
puts "n1:'$n1', n2:'$n2', u1:'$u1', u2:'$u2'"
}
The unnamed arguments are placed at the end of procedure call, after the named arguments:
my_proc -n1 N1 -n2 N2 U1 U2
-> n1:'N1', n2:'N2', u1:'U1', u2:'U2'
The argument parser considers the first argument that doesn't start with the '-' character as well as all
following arguments as unnamed argument:
my_proc U1 U2
-> n1:'', n2:'', u1:'U1', u2:'U2'
Named arguments can be defined multiple times. If the named argument has the -multiply attribute, all
argument values will be collected in a list. Otherwise, only the last provided attribute value will be
retained:
my_proc -n1 N1 -n2 N2 -n1 M1 U1 U2
-> n1:'M1', n2:'N2', u1:'U1', u2:'U2'
The name of the first unnamed argument has therefore not to start with the '-' character. The unnamed
argument is otherwise considered as name of another named argument. This is especially important if the
first unnamed argument is given by a variable that can contain any character strings:
my_proc -n1 N1 -n2 N2 "->" "<-"
-> my_proc: Argument '->' not known
set U1 "->"
my_proc -n1 N1 -n2 N2 $U1 U2}]
my_proc: Argument '->' not known
The '--' flag allows separating unambiguously the unnamed arguments from the named arguments. All data
after the '--' flag will be considered as unnamed argument:
my_proc -n1 N1 -n2 N2 -- "->" "<-"
-> n1:'N1', n2:'N2', u1:'->', u2:'<-'
set U1 "->"
my_proc -n1 N1 -n2 N2 -- $U1 U2
-> n1:'N1', n2:'N2', u1:'->', u2:'<-'
NAMED ARGUMENTS FIRST, UNNAMED ARGUMENTS LATER (TCL STYLE)
The Tk calling style will be chosen if a procedure is defined while the variable
tepam::named_arguments_first is set to 0, or if the procedure attribute -named_arguments_first has been
set to 0. The following procedure will be used in this section to illustrate this calling style:
set tepam::named_arguments_first 0
tepam::procedure my_proc {
-args {
{-n1 -default ""}
{-n2 -default ""}
{u1}
{u2 -default "" -multiple}
}
} {
puts "n1:'$n1', n2:'$n2', u1:'$u1', u2:'$u2'"
}
The unnamed arguments have to be provided first in this case. The named arguments are provided
afterwards:
my_proc U1 U2 -n1 N1 -n2 N2
-> n1:'N1', n1:'N1', u1:'U1', u2:'U2'
The argument parser will assign to each defined unnamed argument a value before it switches to read the
named arguments. This default behavior changes a bit if there are unnamed arguments that are optional or
that can take multiple values.
An argument value will only be assigned to an unnamed argument that is optional (that has either the
-optional attribute or that has a default value), if the value is not beginning with the '-' character or
if no named arguments are defined. The value that starts with '-' is otherwise considered as the name of
a named argument.
Argument values are assigned to an argument that has the -multiple attribute as long as the parameter
value doesn't starts with the '-' character.
Values that start with the '-' character can therefore not be assigned to optional unnamed arguments,
which restricts the usage of the Tcl procedure calling style. The Tk style may be preferable in some
cases, since it allows separating unambiguously the named arguments from the unnamed ones with the '--'
flag.
Let's explore in a bit less theoretically the ways how the previously defined procedure can be called:
The first example calls the procedure without any parameters, which leads to an error since u1 is a
mandatory argument:
my_proc
-> my_proc: Required argument is missing: u1
The procedure call is valid if one parameter is provided for u1:
my_proc U1
-> n1:'', n2:'', u1:'U1', u2:''
If more parameters are provided that are not starting with the '-' character, they will be attributed to
the unnamed arguments. U2 will receive 3 of these parameters, since it accepts multiple values:
my_proc U1 U2 U3 U4
-> n1:'', n2:'', u1:'U1', u2:'U2 U3 U4'
As soon as one parameter starts with '-' and all unnamed arguments have been assigned, the argument
manager tries to interpret the parameter as name of a named argument. The procedure call will fail if a
value beginning with '-' is assigned to an unnamed argument:
my_proc U1 U2 U3 U4 -U5
-> my_proc: Argument '-U5' not known
The attribution of a parameter to a named argument will fail if there are undefined unnamed (non
optional) arguments. The name specification will in this case simply be considered as a parameter value
that is attributed to the next unnamed argument. This was certainly not the intention in the following
example:
my_proc -n1 N1
-> n1:'', n2:'', u1:'-n1', u2:'N1'
The situation is completely different if values have already been assigned to all mandatory unnamed
arguments. A parameter beginning with the '-' character will in this case be considered as a name
identifier for a named argument:
my_proc U1 -n1 N1
-> n1:'N1', n2:'', u1:'U1', u2:''
No unnamed arguments are allowed behind the named arguments:
my_proc U1 -n1 N1 U2
-> my_proc: Argument 'U2' is not an option
The '--' flag has no special meaning if not all mandatory arguments have got assigned a value. This flag
will simply be attributed to one of the unnamed arguments:
my_proc -- -n1 N1
-> n1:'N1', n2:'', u1:'--', u2:''
But the '--' flag is simply ignored if the argument parser has started to handle the named arguments:
my_proc U1 -- -n1 N1
-> n1:'N1', n2:'', u1:'U1', u2:''
my_proc U1 -n1 N1 -- -n2 N2
-> n1:'N1', n2:'N2', u1:'U1', u2:''
RAW ARGUMENT LIST
It may be necessary sometimes that the procedure body is able to access the entire list of arguments
provided during a procedure call. This can happen via the args variable that contains always the
unprocessed argument list:
tepam::procedure {display_message} {
-args {
{-mtype -choices {Warning Error} -default Warning}
{text -type string -multiple}
}
} {
puts "args: $args"
}
display_message -mtype Warning "It is 7:00"
-> args: -mtype Warning {It is 7:00}
SEE ALSO
tepam(3tcl), tepam::argument_dialogbox(3tcl)
KEYWORDS
argument integrity, argument validation, arguments, procedure, subcommand
CATEGORY
Procedures, arguments, parameters, options
COPYRIGHT
Copyright (c) 2009/2010, Andreas Drollinger
tepam 0.4.0 tepam::procedure(3tcl)