1.153 class syntax_table

Class syntax_table describes syntactical properties of (programming) languages. It is used by class editor and class text_buffer to realise syntax driven editors. Class tokeniser used syntax tables to determine tokens and skip comment.

Syntax-tables are named reusable objects (like -for example- colours or fonts). The default syntax table is named default.

The code below defines a syntax table for PCE/Prolog programs:

?- new(X, syntax_table(prolog)),
   send(X, syntax, '"',  string_quote, '"'),
   send(X, syntax, '''', string_quote, ''''),
   send(X, syntax, @,    symbol),

   send(X, syntax,     '%',  comment_start),
   send(X, add_syntax, '\n', comment_end),
   send(X, add_syntax, '/',  comment_start, '*'),
   send(X, add_syntax, '*',  comment_end, '/').

After this definition, the following call associates this syntax table to an editor (view):

?- new(X, view),
   send(X, syntax, prolog).

1.153.1 Instance variables

syntax_table <- name: name*

Name of the syntax_table. Each table has a unique name. The global hash_table object @syntax_tables maps table names into tables. See also syntax_table<-lookup and syntax_table<-convert.

syntax_table <-> paragraph_end: regex

Regular expression (regex object) that describes the end of a paragraph. This regex is actiavted using regex->match for each start of a physical line and should succeed if the lines separates two paragraphs. The default is’\s *$’, implying a line containing only layout characters.

See also syntax_table->sentence_end. and text_buffer<-scan.

Defaults: The default regex describes an empty line: regex('\s *$').

See also

syntax_table-sentence_end

syntax_table <-> sentence_end: regex

Regular expression (regex object) that describes the end of a sentence. Used by text_buffer<-scan, editor->forward_sentence editor ->backward_sentence' and editor syntax_table->fill‘.

See also

syntax_table-paragraph_end

syntax_table <- size: int

Size of the table. Currently XPCE uses 8-bit characters and this value is thus fixed to 256.

syntax_table-table: alien:ushort *

Vector of bitmasks. Used by syntax_table->syntax, syntax_table->has_syntax, etc. See also syntax_table<-context.

1.153.2 Send methods

syntax_table ->add_syntax: character=char, category=syntax_name, context=[char]

Performs a bitwise or on the table entry, placing the character in multiple categories. If a context is specified it replaces the defined context. See also syntax_table->syntax.

Bugs: A character may be in any number of syntactical categories but only has one context character defined.

See also

syntax_table->syntax

syntax_table ->context: character=char, context=char

Set the context character for the specified (1st) character. Normally the context is specified along with the syntax category using syntax_table->syntax or syntax_table->add_syntax.

syntax_table ->copy: syntax_table

Copy the contents of the argument syntax table. See also syntax_table->initialise.

syntax_table ->has_syntax: character=char, category=syntax_name

Test that character has syntax syntax_name.

syntax_table ->initialise: name=[name]*, prototype=[syntax_table]

Create a named or anonymous (name = @nil) syntax table. Named syntax tables are registered in @syntax_tables for later reuse. If a syntax_table is specified its contents is copied in the new table.

Anonymous tables are not stored in @syntax_tables.

syntax_table ->syntax: character=char, category=syntax_name, context=[char]

Modify entry for specified character. See type<-kind for a description on type char. Type syntax_name is a name_of type that allows for the following syntactical categories.

Category            Context Default table
=========================================
uppercase_letter	--	    A-Z
lowercase_letter	--	    a-z
digit				--		0-9
word_separator		--		_
symbol				--
open_bracket		close	([{
close_bracket		open	}])
end_of_line			--		\C-j
white_space			--		\C-a - \C-i, \C-k - SPC, DEL - M-DEL
string_quote		escape	"'
punctuation			--		!#$%&*+,-./:;<=>?\^|~
end_of_string		--		\C-@
comment_start		end
comment_end			start
letter				--		uppercase_letter|lowercase_letter
word				--		letter|digit|word_separator|symbol
layout				--		end_of_line|white_space

Notes:

string_quote

Context is the character to escape the quote in a string. For most languages this is’\’(backslash), for Prolog this is the quote itself.

comment_start , comment_end

If there is no context this specifies a single-character comment. Otherwise the the context is the second character of the comment start/end sequence. More than 2 character comment delimiters are not supported. See also text_buffer->for_all_comments.

syntax_table->syntax makes the table forget anything defined for this character. syntax_table->add_syntax may be used to specify a character into multiple syntactical categories.

See also text_buffer->syntax and class editor.

See also

syntax_table->add_syntax

1.153.3 Get methods

syntax_table <-comment_end: [1..2] -> name

Return 1 or 2 character long comment end sequence as a name. With the argument omitted, the 1 character long comment end sequence is returned.

Diagnostics: Fails silently if no such comment sequence is defined.

syntax_table <-comment_start: [1..2] -> name

Return 1 or 2 character long comment start sequence as a name. With the argument omitted, the 1 character long comment start sequence is returned.

Diagnostics: Fails silently if no such comment sequence is defined.

syntax_table <-context: character=char -> context=char

Some syntactical categories have a context character associated (see syntax_table->syntax). The context characters are stored in this C-array.

syntax_table <-convert: name -> syntax_table

First performs a lookup in @syntax_tables. When successful, this table is returned. Otherwise it returns a new (default) table. See also syntax_table->initialise.

syntax_table <-lookup: name -> syntax_table

Performs a lookup in @syntax_tables.

syntax_table <-syntax: character=char -> category=name|chain

Return the syntactical category of the character. If the character is in multiple categories a chain with category names is returned. See also syntax_table<-context.