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[ruby/racc] Move document from library directory
https://github.com/ruby/racc/commit/2e8d7d286d
This commit is contained in:
Hiroshi SHIBATA
parent
7217f60bb3
commit
b5b3cd2722
2 changed files with 2 additions and 220 deletions
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@ -37,7 +37,8 @@ DESC
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"lib/racc/parser.rb", "lib/racc/parserfilegenerator.rb",
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"lib/racc/pre-setup", "lib/racc/sourcetext.rb",
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"lib/racc/state.rb", "lib/racc/statetransitiontable.rb",
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"lib/racc/static.rb", "doc/en/NEWS.en.rdoc",
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"lib/racc/static.rb",
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"doc/en/NEWS.en.rdoc", "doc/en/grammar2.en.rdoc",
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"doc/en/grammar.en.rdoc", "doc/ja/NEWS.ja.rdoc",
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"doc/ja/command.ja.html", "doc/ja/debug.ja.rdoc",
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"doc/ja/grammar.ja.rdoc", "doc/ja/index.ja.html",
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@ -1,219 +0,0 @@
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= Racc Grammar File Reference
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== Global Structure
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== Class Block and User Code Block
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There are two blocks on the toplevel. One is the 'class' block, the other is the 'user code'
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block. The 'user code' block MUST be placed after the 'class' block.
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== Comments
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You can insert comments about all places. Two styles of comments can be used, Ruby style '#.....' and C style '/\*......*\/'.
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== Class Block
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The class block is formed like this:
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class CLASS_NAME
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[precedence table]
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[token declarations]
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[expected number of S/R conflicts]
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[options]
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[semantic value conversion]
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[start rule]
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rule
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GRAMMARS
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CLASS_NAME is a name of the parser class. This is the name of the generating parser
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class.
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If CLASS_NAME includes '::', Racc outputs the module clause. For example, writing
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"class M::C" causes the code below to be created:
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module M
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class C
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:
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:
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end
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end
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== Grammar Block
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The grammar block describes grammar which is able to be understood by the parser.
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Syntax is:
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(token): (token) (token) (token).... (action)
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(token): (token) (token) (token).... (action)
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| (token) (token) (token).... (action)
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| (token) (token) (token).... (action)
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(action) is an action which is executed when its (token)s are found.
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(action) is a ruby code block, which is surrounded by braces:
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{ print val[0]
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puts val[1] }
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Note that you cannot use '%' string, here document, '%r' regexp in action.
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Actions can be omitted. When it is omitted, '' (empty string) is used.
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A return value of action is a value of the left side value ($$). It is the value of the
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result, or the returned value by `return` statement.
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Here is an example of the whole grammar block.
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rule
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goal: definition rules source { result = val }
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definition: /* none */ { result = [] }
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| definition startdesig { result[0] = val[1] }
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| definition
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precrule # this line continues from upper line
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{
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result[1] = val[1]
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}
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startdesig: START TOKEN
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You can use the following special local variables in action:
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* result ($$)
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The value of the left-hand side (lhs). A default value is val[0].
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* val ($1,$2,$3...)
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An array of value of the right-hand side (rhs).
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* _values (...$-2,$-1,$0)
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A stack of values. DO NOT MODIFY this stack unless you know what you are doing.
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== Operator Precedence
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This function is equal to '%prec' in yacc.
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To designate this block:
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prechigh
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nonassoc '++'
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left '*' '/'
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left '+' '-'
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right '='
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preclow
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`right` is yacc's %right, `left` is yacc's %left.
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`=` + (symbol) means yacc's %prec:
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prechigh
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nonassoc UMINUS
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left '*' '/'
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left '+' '-'
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preclow
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rule
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exp: exp '*' exp
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| exp '-' exp
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| '-' exp =UMINUS # equals to "%prec UMINUS"
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:
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:
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== expect
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Racc has bison's "expect" directive.
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# Example
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class MyParser
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rule
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expect 3
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:
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:
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This directive declares "expected" number of shift/reduce conflicts. If
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"expected" number is equal to real number of conflicts, Racc does not print
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conflict warning message.
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== Declaring Tokens
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By declaring tokens, you can avoid many meaningless bugs. If declared token
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does not exist or existing token does not decleared, Racc output warnings.
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Declaration syntax is:
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token TOKEN_NAME AND_IS_THIS
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ALSO_THIS_IS AGAIN_AND_AGAIN THIS_IS_LAST
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== Options
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You can write options for Racc command in your Racc file.
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options OPTION OPTION ...
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Options are:
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* omit_action_call
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omits empty action call or not.
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* result_var
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uses local variable "result" or not.
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You can use 'no_' prefix to invert their meanings.
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== Converting Token Symbol
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Token symbols are, as default,
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* naked token string in Racc file (TOK, XFILE, this_is_token, ...)
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--> symbol (:TOK, :XFILE, :this_is_token, ...)
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* quoted string (':', '.', '(', ...)
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--> same string (':', '.', '(', ...)
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You can change this default by "convert" block.
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Here is an example:
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convert
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PLUS 'PlusClass' # We use PlusClass for symbol of `PLUS'
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MIN 'MinusClass' # We use MinusClass for symbol of `MIN'
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end
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We can use almost all ruby value can be used by token symbol,
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except 'false' and 'nil'. These cause unexpected parse error.
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If you want to use String as token symbol, special care is required.
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For example:
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convert
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class '"cls"' # in code, "cls"
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PLUS '"plus\n"' # in code, "plus\n"
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MIN "\"minus#{val}\"" # in code, \"minus#{val}\"
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end
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== Start Rule
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'%start' in yacc. This changes start rule.
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start real_target
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== User Code Block
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"User Code Block" is a Ruby source code which is copied to output. There are
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three user code blocks, "header" "inner" and "footer".
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Format of user code is like this:
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---- header
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ruby statement
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ruby statement
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ruby statement
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---- inner
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ruby statement
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:
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:
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If four '-' exist on the line head, Racc treats it as the beginning of the
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user code block. The name of the user code block must be one word.
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