package reason
Terms for command line arguments.
This module provides functions to define terms that evaluate to the arguments provided on the command line.
Basic constraints, like the argument type or repeatability, are specified by defining a value of type t
. Further contraints can be specified during the conversion to a term.
Argument converters
An argument converter transforms a string argument of the command line to an OCaml value. Predefined converters are provided for many types of the standard library.
type 'a printer = Format.formatter -> 'a -> unit
The type for converted argument printers.
some none c
is like the converter c
except it returns Some
value. It is used for command line arguments that default to None
when absent. none
is what to print to document the absence (defaults to ""
).
Arguments and their information
Argument information defines the man page information of an argument and, for optional arguments, its names. An environment variable can also be specified to read the argument value from if the argument is absent from the command line and the variable is defined.
val env_var : ?docs:string -> ?doc:string -> string -> env
env_var docs doc var
is an environment variables var
. doc
is the man page information of the environment variable; the variables mentioned in info
can be used in this documentation string. doc
defaults to "See option $(opt)."
. docs
is the title of the man page section in which the environment variable will be listed, it defaults to "ENVIRONMENT VARIABLES"
.
info docs docv doc env names
defines information for an argument.
names
defines the names under which an optional argument can be referred to. Strings of length 1
("c"
) define short option names ("-c"
), longer strings ("count"
) define long option names ("--count"
). names
must be empty for positional arguments.
env
defines the name of an environment variable which is looked up for defining the argument if it is absent from the command line. See environment variables for details.
doc
is the man page information of the argument. The variable"$(docv)"
can be used to refer to the value ofdocv
(see below). The variable"$(opt)"
will refer to a long option ofnames
or a short one if there is no long option. The variable"$(env)"
will refer to the environment variable specified byenv
(if any). These functions can help with formatting argument values.docv
is for positional and non-flag optional arguments. It is a variable name used in the man page to stand for their value.docs
is the title of the man page section in which the argument will be listed. For optional arguments this defaults to"OPTIONS"
. For positional arguments this defaults to"ARGUMENTS"
. However a positional argument is only listed if it has both adoc
anddocv
specified.
f & v
is f v
, a right associative composition operator for specifying argument terms.
Optional arguments
The information of an optional argument must have at least one name or Invalid_argument
is raised.
flag i
is a bool
argument defined by an optional flag that may appear at most once on the command line under one of the names specified by i
. The argument holds true
if the flag is present on the command line and false
otherwise.
flag_all
is like flag
except the flag may appear more than once. The argument holds a list that contains one true
value per occurence of the flag. It holds the empty list if the flag is absent from the command line.
vflag v [v
0,i
0;...]
is an 'a
argument defined by an optional flag that may appear at most once on the command line under one of the names specified in the i
k values. The argument holds v
if the flag is absent from the command line and the value v
k if the name under which it appears is in i
k.
Note. Environment variable lookup is unsupported for for these arguments.
vflag_all v l
is like vflag
except the flag may appear more than once. The argument holds the list v
if the flag is absent from the command line. Otherwise it holds a list that contains one corresponding value per occurence of the flag, in the order found on the command line.
Note. Environment variable lookup is unsupported for for these arguments.
opt vopt c v i
is an 'a
argument defined by the value of an optional argument that may appear at most once on the command line under one of the names specified by i
. The argument holds v
if the option is absent from the command line. Otherwise it has the value of the option as converted by c
.
If vopt
is provided the value of the optional argument is itself optional, taking the value vopt
if unspecified on the command line.
opt_all vopt c v i
is like opt
except the optional argument may appear more than once. The argument holds a list that contains one value per occurence of the flag in the order found on the command line. It holds the list v
if the flag is absent from the command line.
Positional arguments
The information of a positional argument must have no name or Invalid_argument
is raised. Positional arguments indexing is zero-based.
pos rev n c v i
is an 'a
argument defined by the n
th positional argument of the command line as converted by c
. If the positional argument is absent from the command line the argument is v
.
If rev
is true
(defaults to false
), the computed position is max-n
where max
is the position of the last positional argument present on the command line.
pos_all c v i
is an 'a list
argument that holds all the positional arguments of the command line as converted by c
or v
if there are none.
pos_left rev n c v i
is an 'a list
argument that holds all the positional arguments as converted by c
found on the left of the n
th positional argument or v
if there are none.
If rev
is true
(defaults to false
), the computed position is max-n
where max
is the position of the last positional argument present on the command line.
pos_right
is like pos_left
except it holds all the positional arguments found on the right of the specified positional argument.
Arguments as terms
required a
is a term that fails if a
's value is None
and evaluates to the value of Some
otherwise. Use this for required positional arguments (it can also be used for defining required optional arguments, but from a user interface perspective this shouldn't be done, it is a contradiction in terms).
non_empty a
is term that fails if a
's list is empty and evaluates to a
's list otherwise. Use this for non empty lists of positional arguments.
last a
is a term that fails if a
's list is empty and evaluates to the value of the last element of the list otherwise. Use this for lists of flags or options where the last occurence takes precedence over the others.
Predefined converters
val bool : bool converter
bool
converts values with bool_of_string
.
val char : char converter
char
converts values by ensuring the argument has a single char.
val int : int converter
int
converts values with int_of_string
.
val nativeint : nativeint converter
nativeint
converts values with Nativeint.of_string
.
val int32 : int32 converter
int32
converts values with Int32.of_string
.
val int64 : int64 converter
int64
converts values with Int64.of_string
.
val float : float converter
float
converts values with float_of_string
.
val string : string converter
string
converts values with the identity function.
val enum : (string * 'a) list -> 'a converter
enum l p
converts values such that unambiguous prefixes of string names in l
map to the corresponding value of type 'a
.
Warning. The type 'a
must be comparable with Pervasives.compare
.
val file : string converter
file
converts a value with the identity function and checks with Sys.file_exists
that a file with that name exists.
val dir : string converter
dir
converts a value with the identity function and checks with Sys.file_exists
and Sys.is_directory
that a directory with that name exists.
val non_dir_file : string converter
non_dir_file
converts a value with the identity function and checks with Sys.file_exists
and Sys.is_directory
that a non directory file with that name exists.
list sep c
splits the argument at each sep
(defaults to ','
) character and converts each substrings with c
.
array sep c
splits the argument at each sep
(defaults to ','
) character and converts each substring with c
.
pair sep c0 c1
splits the argument at the first sep
character (defaults to ','
) and respectively converts the substrings with c0
and c1
.
t3 sep c0 c1 c2
splits the argument at the first two sep
characters (defaults to ','
) and respectively converts the substrings with c0
, c1
and c2
.
val t4 :
?sep:char ->
'a converter ->
'b converter ->
'c converter ->
'd converter ->
('a * 'b * 'c * 'd) converter
t4 sep c0 c1 c2 c3
splits the argument at the first three sep
characters (defaults to ','
) respectively converts the substrings with c0
, c1
, c2
and c3
.
Documentation formatting helpers
doc_alts alts
documents the alternative tokens alts
according the number of alternatives. If quoted
is true
(default) the tokens are quoted. The resulting string can be used in sentences of the form "$(docv) must be %s"
.