ext/ply/example/yply/yparse.py

   1 # parser for Unix yacc-based grammars
   2 #
   3 # Author: David Beazley (dave@dabeaz.com)
   4 # Date  : October 2, 2006
   5
   6 import ylex
   7 tokens = ylex.tokens
   8
   9 from ply import *
  10
  11 tokenlist = []
  12 preclist  = []
  13
  14 emit_code = 1
  15
  16 def p_yacc(p):
  17     '''yacc : defsection rulesection'''
  18
  19 def p_defsection(p):
  20     '''defsection : definitions SECTION
  21                   | SECTION'''
  22     p.lexer.lastsection = 1
  23     print "tokens = ", repr(tokenlist)
  24     print
  25     print "precedence = ", repr(preclist)
  26     print
  27     print "# -------------- RULES ----------------"
  28     print
  29
  30 def p_rulesection(p):
  31     '''rulesection : rules SECTION'''
  32
  33     print "# -------------- RULES END ----------------"
  34     print_code(p[2],0)
  35
  36 def p_definitions(p):
  37     '''definitions : definitions definition
  38                    | definition'''
  39
  40 def p_definition_literal(p):
  41     '''definition : LITERAL'''
  42     print_code(p[1],0)
  43
  44 def p_definition_start(p):
  45     '''definition : START ID'''
  46     print "start = '%s'" % p[2]
  47
  48 def p_definition_token(p):
  49     '''definition : toktype opttype idlist optsemi '''
  50     for i in p[3]:
  51        if i[0] not in "'\"":
  52            tokenlist.append(i)
  53     if p[1] == '%left':
  54         preclist.append(('left',) + tuple(p[3]))
  55     elif p[1] == '%right':
  56         preclist.append(('right',) + tuple(p[3]))
  57     elif p[1] == '%nonassoc':
  58         preclist.append(('nonassoc',)+ tuple(p[3]))
  59
  60 def p_toktype(p):
  61     '''toktype : TOKEN
  62                | LEFT
  63                | RIGHT
  64                | NONASSOC'''
  65     p[0] = p[1]
  66
  67 def p_opttype(p):
  68     '''opttype : '<' ID '>'
  69                | empty'''
  70
  71 def p_idlist(p):
  72     '''idlist  : idlist optcomma tokenid
  73                | tokenid'''
  74     if len(p) == 2:
  75         p[0] = [p[1]]
  76     else:
  77         p[0] = p[1]
  78         p[1].append(p[3])
  79
  80 def p_tokenid(p):
  81     '''tokenid : ID
  82                | ID NUMBER
  83                | QLITERAL
  84                | QLITERAL NUMBER'''
  85     p[0] = p[1]
  86
  87 def p_optsemi(p):
  88     '''optsemi : ';'
  89                | empty'''
  90
  91 def p_optcomma(p):
  92     '''optcomma : ','
  93                 | empty'''
  94
  95 def p_definition_type(p):
  96     '''definition : TYPE '<' ID '>' namelist optsemi'''
  97     # type declarations are ignored
  98
  99 def p_namelist(p):
 100     '''namelist : namelist optcomma ID
 101                 | ID'''
 102
 103 def p_definition_union(p):
 104     '''definition : UNION CODE optsemi'''
 105     # Union declarations are ignored
 106
 107 def p_rules(p):
 108     '''rules   : rules rule
 109                | rule'''
 110     if len(p) == 2:
 111        rule = p[1]
 112     else:
 113        rule = p[2]
 114
 115     # Print out a Python equivalent of this rule
 116
 117     embedded = [ ]      # Embedded actions (a mess)
 118     embed_count = 0
 119
 120     rulename = rule[0]
 121     rulecount = 1
 122     for r in rule[1]:
 123         # r contains one of the rule possibilities
 124         print "def p_%s_%d(p):" % (rulename,rulecount)
 125         prod = []
 126         prodcode = ""
 127         for i in range(len(r)):
 128              item = r[i]
 129              if item[0] == '{':    # A code block
 130                   if i == len(r) - 1:
 131                       prodcode = item
 132                       break
 133                   else:
 134                       # an embedded action
 135                       embed_name = "_embed%d_%s" % (embed_count,rulename)
 136                       prod.append(embed_name)
 137                       embedded.append((embed_name,item))
 138                       embed_count += 1
 139              else:
 140                   prod.append(item)
 141         print "    '''%s : %s'''" % (rulename, " ".join(prod))
 142         # Emit code
 143         print_code(prodcode,4)
 144         print
 145         rulecount += 1
 146
 147     for e,code in embedded:
 148         print "def p_%s(p):" % e
 149         print "    '''%s : '''" % e
 150         print_code(code,4)
 151         print
 152
 153 def p_rule(p):
 154    '''rule : ID ':' rulelist ';' '''
 155    p[0] = (p[1],[p[3]])
 156
 157 def p_rule2(p):
 158    '''rule : ID ':' rulelist morerules ';' '''
 159    p[4].insert(0,p[3])
 160    p[0] = (p[1],p[4])
 161
 162 def p_rule_empty(p):
 163    '''rule : ID ':' ';' '''
 164    p[0] = (p[1],[[]])
 165
 166 def p_rule_empty2(p):
 167    '''rule : ID ':' morerules ';' '''
 168
 169    p[3].insert(0,[])
 170    p[0] = (p[1],p[3])
 171
 172 def p_morerules(p):
 173    '''morerules : morerules '|' rulelist
 174                 | '|' rulelist
 175                 | '|'  '''
 176
 177    if len(p) == 2:
 178        p[0] = [[]]
 179    elif len(p) == 3:
 180        p[0] = [p[2]]
 181    else:
 182        p[0] = p[1]
 183        p[0].append(p[3])
 184
 185 #   print "morerules", len(p), p[0]
 186
 187 def p_rulelist(p):
 188    '''rulelist : rulelist ruleitem
 189                | ruleitem'''
 190
 191    if len(p) == 2:
 192         p[0] = [p[1]]
 193    else:
 194         p[0] = p[1]
 195         p[1].append(p[2])
 196
 197 def p_ruleitem(p):
 198    '''ruleitem : ID
 199                | QLITERAL
 200                | CODE
 201                | PREC'''
 202    p[0] = p[1]
 203
 204 def p_empty(p):
 205     '''empty : '''
 206
 207 def p_error(p):
 208     pass
 209
 210 yacc.yacc(debug=0)
 211
 212 def print_code(code,indent):
 213     if not emit_code: return
 214     codelines = code.splitlines()
 215     for c in codelines:
 216          print "%s# %s" % (" "*indent,c)
 217