BNF Grammar: Difference between revisions
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=={{header|Python}}== |
=={{header|Python}}== |
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The best EBNF syntax so far is at, [http://www.martinrinehart.com/articles/python-grammar.html Python EBNF Syntax] |
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<div style="height:30ex;overflow:scroll"><pre> |
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# Grammar for Python |
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# Note: Changing the grammar specified in this file will most likely |
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# require corresponding changes in the parser module |
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# (../Modules/parsermodule.c). If you can't make the changes to |
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# that module yourself, please co-ordinate the required changes |
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# with someone who can; ask around on python-dev for help. Fred |
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# Drake <fdrake@acm.org> will probably be listening there. |
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# NOTE WELL: You should also follow all the steps listed in PEP 306, |
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# "How to Change Python's Grammar" |
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# Commands for Kees Blom's railroad program |
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#diagram:token NAME |
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#diagram:token NUMBER |
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#diagram:token STRING |
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#diagram:token NEWLINE |
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#diagram:token ENDMARKER |
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#diagram:token INDENT |
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#diagram:output\input python.bla |
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#diagram:token DEDENT |
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#diagram:output\textwidth 20.04cm\oddsidemargin 0.0cm\evensidemargin 0.0cm |
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#diagram:rules |
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# Start symbols for the grammar: |
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# single_input is a single interactive statement; |
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# file_input is a module or sequence of commands read from an input file; |
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# eval_input is the input for the eval() and input() functions. |
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# NB: compound_stmt in single_input is followed by extra NEWLINE! |
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single_input: NEWLINE | simple_stmt | compound_stmt NEWLINE |
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file_input: (NEWLINE | stmt)* ENDMARKER |
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eval_input: testlist NEWLINE* ENDMARKER |
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decorator: '@' dotted_name [ '(' [arglist] ')' ] NEWLINE |
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decorators: decorator+ |
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decorated: decorators (classdef | funcdef) |
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funcdef: 'def' NAME parameters ':' suite |
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parameters: '(' [varargslist] ')' |
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varargslist: ((fpdef ['=' test] ',')* |
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('*' NAME [',' '**' NAME] | '**' NAME) | |
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fpdef ['=' test] (',' fpdef ['=' test])* [',']) |
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fpdef: NAME | '(' fplist ')' |
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fplist: fpdef (',' fpdef)* [','] |
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stmt: simple_stmt | compound_stmt |
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simple_stmt: small_stmt (';' small_stmt)* [';'] NEWLINE |
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small_stmt: (expr_stmt | print_stmt | del_stmt | pass_stmt | flow_stmt | |
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import_stmt | global_stmt | exec_stmt | assert_stmt) |
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expr_stmt: testlist (augassign (yield_expr|testlist) | |
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('=' (yield_expr|testlist))*) |
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augassign: ('+=' | '-=' | '*=' | '/=' | '%=' | '&=' | '|=' | '^=' | |
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'<<=' | '>>=' | '**=' | '//=') |
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# For normal assignments, additional restrictions enforced by the interpreter |
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print_stmt: 'print' ( [ test (',' test)* [','] ] | |
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'>>' test [ (',' test)+ [','] ] ) |
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del_stmt: 'del' exprlist |
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pass_stmt: 'pass' |
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flow_stmt: break_stmt | continue_stmt | return_stmt | raise_stmt | yield_stmt |
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break_stmt: 'break' |
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continue_stmt: 'continue' |
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return_stmt: 'return' [testlist] |
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yield_stmt: yield_expr |
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raise_stmt: 'raise' [test [',' test [',' test]]] |
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import_stmt: import_name | import_from |
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import_name: 'import' dotted_as_names |
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import_from: ('from' ('.'* dotted_name | '.'+) |
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'import' ('*' | '(' import_as_names ')' | import_as_names)) |
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import_as_name: NAME ['as' NAME] |
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dotted_as_name: dotted_name ['as' NAME] |
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import_as_names: import_as_name (',' import_as_name)* [','] |
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dotted_as_names: dotted_as_name (',' dotted_as_name)* |
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dotted_name: NAME ('.' NAME)* |
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global_stmt: 'global' NAME (',' NAME)* |
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exec_stmt: 'exec' expr ['in' test [',' test]] |
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assert_stmt: 'assert' test [',' test] |
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compound_stmt: if_stmt | while_stmt | for_stmt | try_stmt | with_stmt | funcdef | classdef | decorated |
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if_stmt: 'if' test ':' suite ('elif' test ':' suite)* ['else' ':' suite] |
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while_stmt: 'while' test ':' suite ['else' ':' suite] |
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for_stmt: 'for' exprlist 'in' testlist ':' suite ['else' ':' suite] |
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try_stmt: ('try' ':' suite |
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((except_clause ':' suite)+ |
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['else' ':' suite] |
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['finally' ':' suite] | |
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'finally' ':' suite)) |
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with_stmt: 'with' test [ with_var ] ':' suite |
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with_var: 'as' expr |
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# NB compile.c makes sure that the default except clause is last |
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except_clause: 'except' [test [('as' | ',') test]] |
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suite: simple_stmt | NEWLINE INDENT stmt+ DEDENT |
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# Backward compatibility cruft to support: |
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# [ x for x in lambda: True, lambda: False if x() ] |
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# even while also allowing: |
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# lambda x: 5 if x else 2 |
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# (But not a mix of the two) |
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testlist_safe: old_test [(',' old_test)+ [',']] |
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old_test: or_test | old_lambdef |
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old_lambdef: 'lambda' [varargslist] ':' old_test |
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test: or_test ['if' or_test 'else' test] | lambdef |
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or_test: and_test ('or' and_test)* |
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and_test: not_test ('and' not_test)* |
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not_test: 'not' not_test | comparison |
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comparison: expr (comp_op expr)* |
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comp_op: '<'|'>'|'=='|'>='|'<='|'<>'|'!='|'in'|'not' 'in'|'is'|'is' 'not' |
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expr: xor_expr ('|' xor_expr)* |
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xor_expr: and_expr ('^' and_expr)* |
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and_expr: shift_expr ('&' shift_expr)* |
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shift_expr: arith_expr (('<<'|'>>') arith_expr)* |
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arith_expr: term (('+'|'-') term)* |
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term: factor (('*'|'/'|'%'|'//') factor)* |
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factor: ('+'|'-'|'~') factor | power |
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power: atom trailer* ['**' factor] |
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atom: ('(' [yield_expr|testlist_gexp] ')' | |
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'[' [listmaker] ']' | |
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'{' [dictmaker] '}' | |
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'`' testlist1 '`' | |
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NAME | NUMBER | STRING+) |
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listmaker: test ( list_for | (',' test)* [','] ) |
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testlist_gexp: test ( gen_for | (',' test)* [','] ) |
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lambdef: 'lambda' [varargslist] ':' test |
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trailer: '(' [arglist] ')' | '[' subscriptlist ']' | '.' NAME |
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subscriptlist: subscript (',' subscript)* [','] |
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subscript: '.' '.' '.' | test | [test] ':' [test] [sliceop] |
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sliceop: ':' [test] |
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exprlist: expr (',' expr)* [','] |
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testlist: test (',' test)* [','] |
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dictmaker: test ':' test (',' test ':' test)* [','] |
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classdef: 'class' NAME ['(' [testlist] ')'] ':' suite |
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arglist: (argument ',')* (argument [','] |
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|'*' test (',' argument)* [',' '**' test] |
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|'**' test) |
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argument: test [gen_for] | test '=' test # Really [keyword '='] test |
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list_iter: list_for | list_if |
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list_for: 'for' exprlist 'in' testlist_safe [list_iter] |
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list_if: 'if' old_test [list_iter] |
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gen_iter: gen_for | gen_if |
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gen_for: 'for' exprlist 'in' or_test [gen_iter] |
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gen_if: 'if' old_test [gen_iter] |
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testlist1: test (',' test)* |
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# not used in grammar, but may appear in "node" passed from Parser to Compiler |
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encoding_decl: NAME |
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yield_expr: 'yield' [testlist] |
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</pre></div> |
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=={{header|SQL}}== |
=={{header|SQL}}== |