Move all lua related files to lua/ subfolder

Also remove the lexers sub directory from the Lua search path.
As a result we attempt to open fewer files during startup:

 $ strace -e open -o log ./vis +q config.h && wc -l log

In order to avoid having to modifiy all lexers which `require('lexer')`
we instead place a symlink in the top level directory.

 $ ./configure --disable-lua
 $ rm -rf lua

Should result in a source tree with most lua specifc functionality
removed.

1 files changed, 64 insertions, 0 deletions

diff --git a/lua/lexers/prolog.lua b/lua/lexers/prolog.lua
new file mode 100644
index 0000000..bda9b53
--- /dev/null
+++ b/lua/lexers/prolog.lua
@@ -0,0 +1,64 @@
+-- Copyright 2006-2016 Mitchell mitchell.att.foicica.com. See LICENSE.
+-- Prolog LPeg lexer.
+
+local l = require('lexer')
+local token, word_match = l.token, l.word_match
+local P, R, S = lpeg.P, lpeg.R, lpeg.S
+
+local M = {_NAME = 'prolog'}
+
+-- Whitespace.
+local ws = token(l.WHITESPACE, l.space^1)
+
+-- Comments.
+local line_comment = '%' * l.nonnewline^0
+local block_comment = '/*' * (l.any - '*/')^0 * P('*/')^-1
+local comment = token(l.COMMENT, line_comment + block_comment)
+
+-- Strings.
+local sq_str = l.delimited_range("'", true)
+local dq_str = l.delimited_range('"', true)
+local string = token(l.STRING, sq_str + dq_str)
+
+-- Numbers.
+local number = token(l.NUMBER, l.digit^1 * ('.' * l.digit^1)^-1)
+
+-- Keywords.
+local keyword = token(l.KEYWORD, word_match{
+  'module', 'meta_predicate', 'multifile', 'dynamic', 'abolish',
+  'current_output', 'peek_code', 'append', 'current_predicate', 'put_byte',
+  'arg', 'current_prolog_flag', 'put_char', 'asserta', 'assert', 'fail',
+  'put_code', 'assertz', 'findall', 'read', 'at_end_of_stream', 'float',
+  'read_term', 'atom', 'flush_output', 'repeat', 'atom_chars', 'functor',
+  'retract', 'atom_codes', 'get_byte', 'set_input', 'atom_concat', 'get_char',
+  'set_output', 'atom_length', 'get_code', 'set_prolog_flag', 'atomic', 'halt',
+  'set_stream_position', 'bagof', 'integer', 'setof', 'call', 'is',
+  'stream_property', 'catch', 'nl', 'sub_atom', 'char_code', 'nonvar', 'throw',
+  'char_conversion', 'number', 'clause', 'number_chars',
+  'unify_with_occurs_check', 'close', 'number_codes', 'var', 'compound', 'once',
+  'copy_term', 'op', 'write', 'writeln', 'write_canonical', 'write_term',
+  'writeq', 'current_char_conversion', 'open', 'current_input', 'peek_byte',
+  'current_op', 'peek_char', 'false', 'true', 'consult', 'member', 'memberchk',
+  'reverse', 'permutation', 'delete',
+  -- Math.
+  'mod', 'div', 'abs', 'exp', 'ln', 'log', 'sqrt', 'round', 'trunc', 'val',
+  'cos', 'sin', 'tan', 'arctan', 'random', 'randominit'
+})
+
+-- Identifiers.
+local identifier = token(l.IDENTIFIER, l.word)
+
+-- Operators.
+local operator = token(l.OPERATOR, S('-!+\\|=:;&<>()[]{}'))
+
+M._rules = {
+  {'whitespace', ws},
+  {'keyword', keyword},
+  {'identifier', identifier},
+  {'string', string},
+  {'comment', comment},
+  {'number', number},
+  {'operator', operator},
+}
+
+return M