Added lua parser example (see #212)

1 files changed, 256 insertions, 0 deletions

diff --git a/examples/lua_parser.py b/examples/lua_parser.py
new file mode 100644
index 0000000..8348a22
--- /dev/null
+++ b/examples/lua_parser.py
@@ -0,0 +1,256 @@
+#
+# lua_parser.py
+#
+# A simple parser for the Lua language.
+#
+# Copyright 2020, Paul McGuire
+#
+
+"""
+from https://www.lua.org/manual/5.1/manual.html#8
+
+    chunk ::= {stat [`;´]} [laststat [`;´]]
+
+    block ::= chunk
+
+    stat ::=  varlist `=´ explist |
+         functioncall |
+         do block end |
+         while exp do block end |
+         repeat block until exp |
+         if exp then block {elseif exp then block} [else block] end |
+         for Name `=´ exp `,´ exp [`,´ exp] do block end |
+         for namelist in explist do block end |
+         function funcname funcbody |
+         local function Name funcbody |
+         local namelist [`=´ explist]
+
+    laststat ::= return [explist] | break
+
+    funcname ::= Name {`.´ Name} [`:´ Name]
+
+    varlist ::= var {`,´ var}
+
+    var ::=  Name | prefixexp `[´ exp `]´ | prefixexp `.´ Name
+
+    namelist ::= Name {`,´ Name}
+
+    explist ::= {exp `,´} exp
+
+    exp ::=  nil | false | true | Number | String | `...´ | function |
+         prefixexp | tableconstructor | exp binop exp | unop exp
+
+    prefixexp ::= var | functioncall | `(´ exp `)´
+
+    functioncall ::=  prefixexp args | prefixexp `:´ Name args
+
+    args ::=  `(´ [explist] `)´ | tableconstructor | String
+
+    function ::= function funcbody
+
+    funcbody ::= `(´ [parlist] `)´ block end
+
+    parlist ::= namelist [`,´ `...´] | `...´
+
+    tableconstructor ::= `{´ [fieldlist] `}´
+
+    fieldlist ::= field {fieldsep field} [fieldsep]
+
+    field ::= `[´ exp `]´ `=´ exp | Name `=´ exp | exp
+
+    fieldsep ::= `,´ | `;´
+
+    binop ::= `+´ | `-´ | `*´ | `/´ | `^´ | `%´ | `..´ |
+         `<´ | `<=´ | `>´ | `>=´ | `==´ | `~=´ |
+         and | or
+
+    unop ::= `-´ | not | `#´
+
+"""
+import pyparsing as pp
+
+ppc = pp.pyparsing_common
+pp.ParserElement.enablePackrat()
+
+LBRACK, RBRACK, LBRACE, RBRACE, LPAR, RPAR, EQ, COMMA, SEMI, COLON = map(
+    pp.Suppress, "[]{}()=,;:"
+)
+OPT_SEMI = pp.Optional(SEMI).suppress()
+ELLIPSIS = pp.Literal("...")
+keywords = {
+    k.upper(): pp.Keyword(k)
+    for k in """\
+    return break do end while if then elseif else for in function local repeat until nil false true and or not
+    """.split()
+}
+vars().update(keywords)
+
+comment_intro = pp.Literal("--")
+short_comment = comment_intro + pp.restOfLine
+long_comment = comment_intro + LBRACK + ... + RBRACK
+lua_comment = long_comment | short_comment
+
+ident = ppc.identifier
+name = pp.delimitedList(ident, delim=".", combine=True)
+
+namelist = pp.delimitedList(name)
+number = ppc.number
+
+# does not parse levels
+multiline_string = pp.QuotedString("[[", endQuoteChar="]]", multiline=True)
+string = pp.QuotedString("'") | pp.QuotedString('"') | multiline_string
+
+exp = pp.Forward()
+
+#     explist1 ::= {exp ','} exp
+explist1 = pp.delimitedList(exp)
+
+stat = pp.Forward()
+
+#    laststat ::= return [explist1]  |  break
+laststat = pp.Group(RETURN + explist1) | BREAK
+
+#    block ::= {stat [';']} [laststat[';']]
+block = pp.Group(stat + OPT_SEMI)[1, ...] + pp.Optional(laststat)
+
+#    field ::= '[' exp ']' '=' exp  |  Name '=' exp  |  exp
+field = pp.Group(
+    LBRACK + exp + RBRACK + EQ + pp.Group(exp) | name + EQ + pp.Group(exp) | exp
+)
+
+#    fieldsep ::= ','  |  ';'
+fieldsep = COMMA | SEMI
+
+#    fieldlist ::= field {fieldsep field} [fieldsep]
+field_list = pp.delimitedList(field, delim=fieldsep) + pp.Optional(fieldsep)
+
+#    tableconstructor ::= '{' [fieldlist] '}'
+tableconstructor = pp.Group(LBRACE + pp.Optional(field_list) + RBRACE)
+
+#    parlist1 ::= namelist [',' '...']  |  '...'
+parlist = namelist + pp.Optional(COMMA + ELLIPSIS) | ELLIPSIS
+
+#    funcname ::= Name {'.' Name} [':' Name]
+funcname = pp.Group(name + COLON + name) | name
+
+#    function ::= function funcbody
+#    funcbody ::= '(' [parlist1] ')' block end
+funcbody = pp.Group(LPAR + parlist + RPAR) + block + END
+function = FUNCTION + funcbody
+
+#    args ::=  '(' [explist1] ')'  |  tableconstructor  |  String
+args = LPAR + pp.Optional(explist1) + RPAR | tableconstructor | string
+
+# this portion of the spec is left-recursive, must break LR loop
+#    varlist1 ::= var {',' var}
+#    var ::=  Name  |  prefixexp '[' exp ']'  |  prefixexp '.' Name
+#    prefixexp ::= var  |  functioncall  |  '(' exp ')'
+#    functioncall ::=  prefixexp args  |  prefixexp ':' Name args
+
+prefixexp = name | LPAR + exp + RPAR
+functioncall = prefixexp + args | prefixexp + COLON + name + args
+var = pp.Forward()
+var_atom = functioncall | name | LPAR + exp + RPAR
+index_ref = pp.Group(LBRACK + exp + RBRACK)
+var <<= pp.delimitedList(pp.Group(var_atom + index_ref) | var_atom, delim=".")
+
+varlist1 = pp.delimitedList(var)
+
+# exp ::=  nil  |  false  |  true  |  Number  |  String  |  '...'  |
+#              function  |  prefixexp  |  tableconstructor
+exp_atom = (
+    NIL
+    | FALSE
+    | TRUE
+    | number
+    | string
+    | ELLIPSIS
+    | functioncall
+    | var  # prefixexp
+    | tableconstructor
+)
+
+exp <<= pp.infixNotation(
+    exp_atom,
+    [
+        (pp.oneOf("+ -"), 2, pp.opAssoc.LEFT),
+        (AND, 2, pp.opAssoc.LEFT),
+        (OR, 2, pp.opAssoc.LEFT),
+    ],
+)
+
+assignment_stat = pp.Optional(LOCAL) + varlist1 + EQ + explist1
+func_call_stat = pp.Optional(LOCAL) + functioncall
+do_stat = DO + block + END
+while_stat = WHILE + exp + block + END
+repeat_stat = REPEAT + block + UNTIL + exp
+for_loop_stat = (
+    FOR + name + EQ + exp + COMMA + exp + pp.Optional(COMMA + exp) + DO + block + END
+)
+for_seq_stat = FOR + namelist + IN + explist1 + DO + block + END
+if_stat = (
+    IF
+    + exp
+    + THEN
+    + block
+    + pp.Group(ELSEIF + exp + THEN + block)[...]
+    + pp.Optional(pp.Group(ELSE + block))
+    + END
+)
+function_def = pp.Optional(LOCAL) + FUNCTION + funcname + funcbody
+
+for var_name in """
+        assignment_stat
+        func_call_stat
+        do_stat
+        while_stat
+        repeat_stat
+        for_loop_stat
+        for_seq_stat
+        if_stat
+        function_def
+        """.split():
+    vars()[var_name].setName(var_name)
+
+#    stat ::=  varlist1 '=' explist1  |
+#              functioncall  |
+#              do block end  |
+#              while exp do block end  |
+#              repeat block until exp  |
+#              if exp then block {elseif exp then block} [else block] end  |
+#              for Name '=' exp ',' exp [',' exp] do block end  |
+#              for namelist in explist1 do block end  |
+#              function funcname funcbody  |
+#              local function Name funcbody  |
+#              local namelist ['=' explist1]
+stat <<= pp.Group(
+    assignment_stat
+    | do_stat
+    | while_stat
+    | repeat_stat
+    | for_loop_stat
+    | for_seq_stat
+    | func_call_stat
+    | if_stat
+)
+
+# ignore comments
+function_def.ignore(lua_comment)
+
+if __name__ == "__main__":
+
+    sample = r"""
+    function test(x)
+        local t = {foo=1, bar=2, arg=x}
+        n = 0
+        if t['foo'] then
+            n = n + 1
+        end
+    end
+    """
+
+    try:
+        result = function_def.parseString(sample)
+        result.pprint()
+    except pp.ParseException as pe:
+        print(pe.explain())