97:
32:
310:(CFG). However, there are often aspects of programming languages that a CFG can't express, but are part of the language and are documented in its specification. These are details that require a context to determine their validity and behaviour. For example, if a language allows new types to be declared, a CFG cannot predict the names of such types nor the way in which they should be used. Even if a language has a predefined set of types, enforcing proper usage usually requires some context. Another example is
386:
AST differencing, or for short tree differencing, consists of computing the list of differences between two ASTs. This list of differences is typically called an edit script. The edit script directly refers to the AST of the code. For instance, an edit action may result in the addition of a new AST
357:
To support compiler verification it should be possible to unparse an AST into source code form. The source code produced should be sufficiently similar to the original in appearance and identical in execution, upon recompilation. The AST is used intensively during
297:
An AST usually contains extra information about the program, due to the consecutive stages of analysis by the compiler. For example, it may store the position of each element in the source code, allowing the compiler to print useful error
286:
An AST can be edited and enhanced with information such as properties and annotations for every element it contains. Such editing and annotation is impossible with the source code of a program, since it would imply changing
223:
are implicit in the tree structure, so these do not have to be represented as separate nodes. Likewise, a syntactic construct like an if-condition-then statement may be denoted by means of a single node with three branches.
349:
Some operations will always require two elements, such as the two terms for addition. However, some language constructs require an arbitrarily large number of children, such as argument lists passed to programs from the
274:
phase of a compiler. It often serves as an intermediate representation of the program through several stages that the compiler requires, and has a strong impact on the final output of the compiler.
219:
The syntax is "abstract" in the sense that it does not represent every detail appearing in the real syntax, but rather just the structural or content-related details. For instance, grouping
737:: The JavaParser library provides you with an Abstract Syntax Tree of your Java code. The AST structure then allows you to work with your Java code in an easy programmatic way.
743:: A library to analyze, transform, rewrite, and transpile Java source code. It parses source files to build a well-designed AST with powerful analysis and transformation API.
369:
After verifying correctness, the AST serves as the base for code generation. The AST is often used to generate an intermediate representation (IR), sometimes called an
354:. As a result, an AST used to represent code written in such a language has to also be flexible enough to allow for quick addition of an unknown quantity of children.
61:
774:
573:
83:
366:
based on the AST during semantic analysis. A complete traversal of the tree allows verification of the correctness of the program.
1023:
992:
997:
645:
444:
362:, where the compiler checks for correct usage of the elements of the program and the language. The compiler also generates
359:
240:
711:
1002:
671:
449:
96:
940:
842:
1028:
44:
837:
809:
667:
464:
54:
48:
40:
678:
945:
888:
847:
728:
485:
470:
408:
619:
602:
427:
251:
65:
749:: A website to help visualize ASTs in several popular languages such as Go, Python, Java, and JavaScript.
634:
294:, an AST does not include inessential punctuation and delimiters (braces, semicolons, parentheses, etc.).
239:
process. Once built, additional information is added to the AST by means of subsequent processing, e.g.,
970:
950:
814:
767:
433:
370:
197:
326:
The design of an AST is often closely linked with the design of a compiler and its expected features.
315:
307:
987:
955:
893:
871:
624:
303:
101:
690:
919:
663:
579:
534:
422:
212:. Each node of the tree denotes a construct occurring in the text. It is sometimes called just a
965:
909:
826:
569:
526:
417:
227:
This distinguishes abstract syntax trees from concrete syntax trees, traditionally designated
333:
Variable types must be preserved, as well as the location of each declaration in source code.
861:
791:
760:
561:
518:
306:
by nature. In order to avoid this ambiguity, programming languages are often specified as a
247:
193:
701:
439:
396:
271:
263:
209:
201:
339:
Left and right components of binary operations must be stored and correctly identified.
1017:
883:
799:
351:
282:
An AST has several properties that aid the further steps of the compilation process:
538:
507:"Change Distilling:Tree Differencing for Fine-Grained Source Code Change Extraction"
914:
723:"Architecture‑Driven Modernization — ADM: Abstract Syntax Tree Metamodeling — ASTM"
583:
475:
363:
336:
The order of executable statements must be explicitly represented and well defined.
659:
318:
is yet another case where correct usage and final function are context-dependent.
960:
866:
311:
291:
270:
to represent the structure of program code. An AST is usually the result of the
205:
342:
Identifiers and their assigned values must be stored for assignment statements.
977:
876:
455:
452:, a family of languages written in trees, with macros to manipulate code trees
228:
20:
530:
856:
804:
705:
506:
267:
522:
553:
565:
346:
These requirements can be used to design the data structure for the AST.
236:
783:
616:
Understanding Source Code
Evolution Using Abstract Syntax Tree Matching
220:
16:
Tree representation of the abstract syntactic structure of source code
752:
480:
232:
679:"Abstract Syntax Tree and Java Code Manipulation in the Eclipse IDE"
614:
Neamtiu, Iulian; Foster, Jeffrey S.; Hicks, Michael (May 17, 2005).
505:
Fluri, Beat; Wursch, Michael; PInzger, Martin; Gall, Harald (2007).
740:
636:
Improving
Abstract Syntax Tree based Source Code Change Detection
196:
to represent the structure of a program or code snippet. It is a
722:
314:, where the type of an element can change depending on context.
756:
25:
610:(overview of AST implementation in various language families)
746:
734:
552:
Koschke, Rainer; Falke, Raimar; Frenzel, Pierre (2006).
646:"Thoughts on the Visual C++ Abstract Syntax Tree (AST)"
100:
An abstract syntax tree for the following code for the
554:"Clone Detection Using Abstract Syntax Suffix Trees"
933:
902:
825:
790:
558:
2006 13th
Working Conference on Reverse Engineering
395:An AST is a powerful abstraction to perform code
53:but its sources remain unclear because it lacks
768:
8:
603:"Abstract Syntax Tree Implementation Idioms"
775:
761:
753:
712:"Abstract Syntax Tree Metamodel Standard"
623:
511:IEEE Transactions on Software Engineering
329:Core requirements include the following:
84:Learn how and when to remove this message
95:
497:
246:Abstract syntax trees are also used in
235:during the source code translation and
231:. Parse trees are typically built by a
19:For the trees used in linguistics, see
618:. MSR'05. Saint Louis, Missouri: ACM.
7:
14:
486:Abstract Syntax Tree Interpreters
993:History of compiler construction
30:
998:Comparison of parser generators
644:Lucas, Jason (16 August 2006).
387:node representing a function.
192:) is a data structure used in
1:
1003:Operator-precedence grammar
373:, for the code generation.
1045:
560:. IEEE. pp. 253–262.
262:Abstract syntax trees are
18:
445:Extended Backus–Naur form
204:structure of text (often
465:Semantic resolution tree
258:Application in compilers
105:
39:This article includes a
1024:Trees (data structures)
946:Definite clause grammar
704:: Abstract Syntax Tree
471:Shunting-yard algorithm
409:Abstract semantic graph
68:more precise citations.
523:10.1109/tse.2007.70731
428:Directed acyclic graph
252:program transformation
200:representation of the
181:
951:Deterministic parsing
691:"CAST representation"
434:Document Object Model
371:intermediate language
99:
674:abstract syntax tree
566:10.1109/wcre.2006.18
460:concrete syntax tree
316:Operator overloading
308:context-free grammar
302:Languages are often
186:abstract syntax tree
988:Scannerless parsing
956:Dynamic programming
411:(ASG), also called
241:contextual analysis
102:Euclidean algorithm
784:Parsing algorithms
423:Control-flow graph
202:abstract syntactic
182:
41:list of references
1011:
1010:
810:Recursive descent
639:(Diploma thesis).
633:WĂĽrsch, Michael.
418:Composite pattern
360:semantic analysis
94:
93:
86:
1036:
1029:Formal languages
966:Parser generator
889:Recursive ascent
777:
770:
763:
754:
726:
718:
716:
698:
686:
649:
640:
629:
627:
609:
607:
588:
587:
549:
543:
542:
502:
458:, also known as
382:AST differencing
290:Compared to the
248:program analysis
194:computer science
178:
175:
172:
169:
166:
163:
160:
157:
154:
151:
148:
145:
142:
139:
136:
133:
130:
127:
124:
121:
118:
115:
112:
109:
89:
82:
78:
75:
69:
64:this article by
55:inline citations
34:
33:
26:
1044:
1043:
1039:
1038:
1037:
1035:
1034:
1033:
1014:
1013:
1012:
1007:
929:
898:
821:
786:
781:
721:
714:
710:
689:
677:
656:
643:
632:
613:
605:
600:
597:
595:Further reading
592:
591:
576:
551:
550:
546:
517:(11): 725–743.
504:
503:
499:
494:
440:Expression tree
405:
397:clone detection
393:
391:Clone detection
384:
379:
324:
280:
272:syntax analysis
266:widely used in
264:data structures
260:
210:formal language
208:) written in a
180:
179:
176:
173:
170:
167:
164:
161:
158:
155:
152:
149:
146:
143:
140:
137:
134:
131:
128:
125:
122:
119:
116:
113:
110:
107:
90:
79:
73:
70:
59:
45:related reading
35:
31:
24:
17:
12:
11:
5:
1042:
1040:
1032:
1031:
1026:
1016:
1015:
1009:
1008:
1006:
1005:
1000:
995:
990:
985:
980:
975:
974:
973:
963:
958:
953:
948:
943:
937:
935:
934:Related topics
931:
930:
928:
927:
924:
923:
922:
912:
906:
904:
900:
899:
897:
896:
891:
886:
881:
880:
879:
874:
869:
864:
854:
853:
852:
851:
850:
840:
831:
829:
823:
822:
820:
819:
818:
817:
815:Tail recursive
807:
802:
796:
794:
788:
787:
782:
780:
779:
772:
765:
757:
751:
750:
744:
738:
732:
719:
708:
699:
687:
675:
655:
654:External links
652:
651:
650:
641:
630:
625:10.1.1.88.5815
611:
596:
593:
590:
589:
574:
544:
496:
495:
493:
490:
489:
488:
483:
478:
473:
468:
462:
453:
447:
442:
437:
431:
425:
420:
415:
404:
401:
392:
389:
383:
380:
378:
375:
344:
343:
340:
337:
334:
323:
320:
300:
299:
295:
288:
279:
276:
259:
256:
106:
92:
91:
49:external links
38:
36:
29:
15:
13:
10:
9:
6:
4:
3:
2:
1041:
1030:
1027:
1025:
1022:
1021:
1019:
1004:
1001:
999:
996:
994:
991:
989:
986:
984:
981:
979:
976:
972:
969:
968:
967:
964:
962:
959:
957:
954:
952:
949:
947:
944:
942:
939:
938:
936:
932:
925:
921:
918:
917:
916:
913:
911:
908:
907:
905:
901:
895:
892:
890:
887:
885:
882:
878:
875:
873:
870:
868:
865:
863:
860:
859:
858:
855:
849:
848:Shunting-yard
846:
845:
844:
841:
839:
836:
835:
833:
832:
830:
828:
824:
816:
813:
812:
811:
808:
806:
803:
801:
798:
797:
795:
793:
789:
785:
778:
773:
771:
766:
764:
759:
758:
755:
748:
745:
742:
739:
736:
733:
730:
724:
720:
713:
709:
707:
703:
700:
696:
692:
688:
684:
680:
676:
673:
669:
665:
661:
658:
657:
653:
647:
642:
638:
637:
631:
626:
621:
617:
612:
604:
601:Jones, Joel.
599:
598:
594:
585:
581:
577:
575:0-7695-2719-1
571:
567:
563:
559:
555:
548:
545:
540:
536:
532:
528:
524:
520:
516:
512:
508:
501:
498:
491:
487:
484:
482:
479:
477:
474:
472:
469:
466:
463:
461:
457:
454:
451:
448:
446:
443:
441:
438:
435:
432:
429:
426:
424:
421:
419:
416:
414:
410:
407:
406:
402:
400:
398:
390:
388:
381:
376:
374:
372:
367:
365:
364:symbol tables
361:
355:
353:
352:command shell
347:
341:
338:
335:
332:
331:
330:
327:
321:
319:
317:
313:
309:
305:
296:
293:
289:
285:
284:
283:
277:
275:
273:
269:
265:
257:
255:
253:
249:
244:
242:
238:
234:
230:
225:
222:
217:
215:
211:
207:
203:
199:
195:
191:
187:
103:
98:
88:
85:
77:
74:February 2013
67:
63:
57:
56:
50:
46:
42:
37:
28:
27:
22:
982:
903:Mixed, other
894:Shift-reduce
747:AST Explorer
694:
682:
635:
615:
557:
547:
514:
510:
500:
476:Symbol table
459:
412:
394:
385:
377:Other usages
368:
356:
348:
345:
328:
325:
301:
281:
261:
245:
226:
218:
213:
189:
185:
183:
80:
71:
60:Please help
52:
961:Memoization
926:Statistical
920:Left corner
877:Generalized
834:Precedence
702:eli project
695:cs.utah.edu
683:eclipse.org
312:duck typing
292:source code
229:parse trees
221:parentheses
214:syntax tree
206:source code
66:introducing
1018:Categories
978:Parse tree
910:Combinator
867:Look-ahead
735:JavaParser
731:standard).
666:plugin to
492:References
456:Parse tree
413:term graph
278:Motivation
21:parse tree
872:Canonical
827:Bottom-up
706:Unparsing
668:visualize
620:CiteSeerX
531:0098-5589
304:ambiguous
298:messages.
268:compilers
254:systems.
237:compiling
843:Operator
792:Top-down
660:AST View
539:13659557
403:See also
664:Eclipse
584:6985484
62:improve
862:Simple
838:Simple
800:Earley
622:
582:
572:
537:
529:
481:TreeDL
322:Design
233:parser
174:return
915:Chart
741:Spoon
715:(PDF)
662:: an
606:(PDF)
580:S2CID
535:S2CID
467:(SRT)
436:(DOM)
430:(DAG)
108:while
47:, or
971:LALR
672:Java
570:ISBN
527:ISSN
450:Lisp
250:and
198:tree
153:else
129:>
983:AST
941:PEG
884:CYK
729:OMG
562:doi
519:doi
287:it.
190:AST
184:An
1020::
857:LR
805:LL
693:.
681:.
670:a
578:.
568:.
556:.
533:.
525:.
515:33
513:.
509:.
399:.
243:.
216:.
162::=
141::=
123:if
51:,
43:,
776:e
769:t
762:v
727:(
725:.
717:.
697:.
685:.
648:.
628:.
608:.
586:.
564::
541:.
521::
188:(
177:a
171:a
168:-
165:b
159:b
156::
150:b
147:-
144:a
138:a
135::
132:b
126:a
120::
117:0
114:â‰
111:b
104::
87:)
81:(
76:)
72:(
58:.
23:.
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
