lean2/doc/server.org

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Lean can process input incrementally, and extract type information.
This feature is useful for implementing "intelligent" support for Lean
in editors such as Emacs. It provides a convenient way to access
descriptions of functions, overloaded symbols, and typing information.
We must use the option =--server= to enable this feature.
* Commands
Lean implements a simple set of commands for loading files, extracting
typing information, and "replacing" lines. The commands should be sent
to the standard input.
** Load file
#+BEGIN_SRC
LOAD [file-name]
#+END_SRC
This command loads the Lean file named =[file-name]=.
Lean will create a "snapshot" (aka backtracking point) after each
command. Lean uses the "snapshots" to process incremental updates efficiently.
** Visit file
#+BEGIN_SRC
VISIT [file-name]
#+END_SRC
Lean can keep information about multiple files. This command
sets =[file-name]= as the "current" file. The remaining commands
are all with respect to the current file. If =[file-name]= has not been
loaded yet, then this command will load it. Some of the remaining commands
apply "changes" to the current file. The =LOAD= command can be used to
discard all these changes, and enforce the content of the file stored
in file system.
** Replace line
#+BEGIN_SRC
REPLACE [line-number]
[new-line]
#+END_SRC
This command replaces the line =[line-number]= (in the current file) with =[new-line]=.
Lean uses the snapshots to process the request efficiently.
If =[line-number]= is greater than the total number of lines in the lean
buffer, then empty lines are introduced. The lines are indexed from 1.
** Insert line
#+BEGIN_SRC
INSERT [line-number]
[new-line]
#+END_SRC
This command inserts =[new-line]= (in the current file) before line =[line-number]=.
If =[line-number]= is greater than the total number of lines in the lean
buffer, then empty lines are introduced. The lines are indexed from 1.
** Remove line
#+BEGIN_SRC
REMOVE [line-number]
#+END_SRC
Remove line =[line-number]= (in the current file). The lines are indexed from 1.
If =[line-number]= is greater than the total number of lines in the lean
buffer, then the command is ignored.
** Extracting information
#+BEGIN_SRC
INFO [line-number] [column-number]?
#+END_SRC
This command extracts typing information associated with line
=[line-number]= (in the current file) and =[column-number]=.
If =[column-number]= is not provided then (potentially) long
information is not included.
Lean produces a possible empty sequence of entries delimited by the lines
=-- BEGININFO= and =-- ENDINFO=.
#+BEGIN_SRC
-- BEGININFO
[entries]*
-- ENDINFO
#+END_SRC
If the server is still busy processing a previously requested update, then it
produces the output
#+BEGIN_SRC
-- BEGININFO
-- NAY
-- ENDINFO
#+END_SRC
where =NAY= stands for "not available yet".
A type information entry is of the form
#+BEGIN_SRC
-- TYPE|[line-number]|[column-number]
[type]
-- ACK
#+END_SRC
Information for overloaded operators and symbols is of the form
#+BEGIN_SRC
-- OVERLOAD|[line-number]|[column-number]
[overload-1]
--
...
--
[overload-n]
-- ACK
#+END_SRC
Information for synthesized placeholders is of the form
#+BEGIN_SRC
-- SYNTH|[line-number]|[column-number]
[synthesized-term]
-- ACK
#+END_SRC
The following two information entries provide information for Lean keywords/symbols and identifiers.
#+BEGIN_SRC
-- SYMBOL|[line-number]|[column-number]
[symbol]
-- ACK
#+END_SRC
#+BEGIN_SRC
-- IDENTIFIER|[line-number]|[column-number]
[fully-qualified-name]
-- ACK
#+END_SRC
Information about introduced coercions is of the form
#+BEGIN_SRC
-- COERCION|[line-number]|[column-number]
[coercion-application]
--
[result-type]
-- ACK
#+END_SRC
When =[column-number]= is provided in the =INFO= command, the type of terms surrounded by =()=
is also included. The ouput has the form
#+BEGIN_SRC
-- EXTRA_TYPE|[line-number]|[column-number]
[term]
--
[type]
-- ACK
#+END_SRC
Here is an example of output produced by Lean
#+BEGIN_SRC
-- BEGININFO
-- TYPE|15|38
num
-- ACK
-- TYPE|15|40
num → num → Prop
-- ACK
-- OVERLOAD|15|42
f
--
foo.f
-- ACK
-- TYPE|15|42
num → num
-- ACK
-- TYPE|15|44
num
-- ACK
-- IDENTIFIER|15|42
foo.f
-- ACK
-- ENDINFO
#+END_SRC
** Check line
As described above, several commands can be used to apply
modifications to opened/visited files. These modification reflect
modifications performed by the text editor. The command =CHECK= can be
used to double check whether the text editor and Lean have the "same
view" of the current file + modifications.
The following commands returns =-- OK= if the line =[line-number]= in
the current file is =[line]=. It returns =-- MISMATCH line out of
range=, if =[line-number]= is too big, and =-- MISMATCH expected
[lean-line]= when there is a mismatch, and Lean expects
=[line-number]= to be =[lean-line]=.
#+BEGIN_SRC
-- CHECK [line-number]
[line]
#+END_SRC
** Set configuration option
The command
#+BEGIN_SRC
-- SET
[option-name] [value]
#+END_SRC
sets a Lean options, =[option-name]= must be a valid Lean option.
Any option that can be set using the command =set_option= in a '.lean'
file is supported.
This command produces the output
#+BEGIN_SRC
-- BEGINSET
[error]?
-- ENDSET
#+END_SRC
where the line =[error]?= is printed if there are errors parsing the
=SET= command (e.g., invalid option name).
Here is an example that forces the Lean pretty printer to display
implicit arguments.
#+BEGIN_SRC
-- SET
pp.implicit true
#+END_SRC
** Eval
The following command evaluates a Lean command. It has the effect of
evaluating a command in the end of the current file
#+BEGIN_SRC
-- EVAL
[command]
#+END_SRC
This command produces the output
#+BEGIN_SRC
-- BEGINEVAL
[error]/[output]
-- ENDEVAL
#+END_SRC
Here is an example that executes the =check= command to obtain the
type of =Prop=.
#+BEGIN_SRC
-- EVAL
check Prop
#+END_SRC
If the server is still busy processing a previously requested update, then it
produces the output
#+BEGIN_SRC
-- BEGINEVAL
-- NAY
-- ENDEVAL
#+END_SRC
** Wait
The following command is for debugging purposes. It blocks the server
until all pending information has been computed.
#+BEGIN_SRC
WAIT
#+END_SRC
** Options
The command =OPTIONS= display all configuration options available
in Lean. It has the form
#+BEGIN_SRC
OPTIONS
#+END_SRC
The output is a sequence of entries
#+BEGIN_SRC
-- BEGINOPTIONS
[entry]*
-- ENDOPTIONS
#+END_SRC
where each entry is of the form
#+BEGIN_SRC
-- [name]|[kind]|[default-value]|[description]
#+END_SRC
The available =kinds= are: =Bool=, =Int=, =Unsigned Int=, =Double=,
=String=, and =S-Expressions=.
** Find pattern
Given a sequence of characters, the command =FINDP= uses string fuzzy matching to
find declarations in the environment. The procedure uses [Bitap algorithm](http://en.wikipedia.org/wiki/Bitap_algorithm).
The approximate match is defined in terms of [Levenshtein distance](http://en.wikipedia.org/wiki/Levenshtein_distance).
The matches are sorted based on this distance.
#+BEGIN_SRC
FINDP [line-number]
[pattern]
#+END_SRC
The line number =[line-number]= is used to select the environment object that will be used to perform the search.
Only declarations in the environment are considered by =FINDP=.
The output has the following form
#+BEGIN_SRC
-- BEGINFINDP [NAY]? [STALE]?
[entries]*
-- ENDFINDP
#+END_SRC
The modifier =NAY= is included when the environment object for the given line is not available yet.
The modifier =STALE= is included to indicate that an environment object is being used, but it
does not contain the latest changes.
The entries are of the form
#+BEGIN_SRC
[name]|[type]
#+END_SRC
The types are printed without using line breaks.
The command =FINDP= is mainly used to implement auto-completion.
** Find declarations for "placeholder/goal"
A declaration may contain placeholders/goals =_=. Some of these placeholders are instantiated automatically by Lean.
Others, must be manually filled by the user. The command =FINDG= generates a sequence of declarations that may be used to
"fill" a particular placeholder. This command is only available if the declaration containing =_= is type correct, and
lean "knows" what is the expected type for =_=.
#+BEGIN_SRC
FINDG [line-number] [column-number]
[filters]*
#+END_SRC
The character at the given =[line-number]= and =[column-number]= must be a =_=.
The command also accepts a sequence of filters of the form =+[id_1]= and =-[id_2]=.
Lean will only consider declarations whose name contains =id_1= and does not contain =id_2=.
Here is an example:
#+BEGIN_SRC
FINDG 48 10
+intro -and -elim
#+END_SRC
For the command above, lean will print any declaration whose resultant type matches the type expected by =_=, and
whose name contains =intro= but does not contain =and= and =elim=.
Lean does not display "trivial" matches. We say a match is trivial if the resultant type of a declaration
matches anything.
The output produced by =FINDG= uses the same format used by =FINDP=.