Implementing "++" operator, stepping into parse.y

*NQMFNFOUJOH PQFSBUPS TUFQQJOHJOUPQBSTFZ .JTBLJ4IJPJ !TIJPJNN!DPF@ .BZ 3VCZ,BJHJ

"CPVUNF (JU)VC!TIJPJNN 5XJUUFS!DPF@ 8FCBQQMJDBUJPOEFWFMPQFSBU4.4$P -UE .FNCFSPG"TBLVTBSC'VLVPLBSC "NJOUFSFTUFEJOOFUXPSLJOHBOEQBSTJOH

)BWFZPVFWFSXJTIFE 3VCZIBEJODSFNFOUEFDSFNFOUPQFSBUPST i = 0 while i < 100
i++ puts "FizzBuzz" if i % 15 == 0 puts "Fizz" if i % 3 == 0 puts "Buzz" if i % 5 == 0 end 'PSFYBNQMF

8IZEPFTOU3VCZIBWFBOJODSFNFOUPQFSBUPS .PTUQFPQMFIBWFQSPCBCMZXPOEFSFEBCPVUUIJT BUMFBTUPODF

.BU[TUBUFTUIFSFBTPOGPSUIJT :PVDBOUEF fi OFPCKFDUPSJFOUFETFNBOUJDT GPSJODSFNFOUEFDSFNFOUPQFSBUJPOT SFGIUUQTCVHTSVCZMBOHPSHJTTVFT

4PXJUIUIFDVSSFOU.3* JGXFUSZUPFYFDVUFBTDSJQUMJLFAJ A # test.rb i =
0 i++

ʜJUDBVTFTBTZOUBYFSSPSBUQBSTJOH # test.rb i = 0 i++ SVCZUFTUSC J J
UFTUSCTZOUBYFSSPS VOFYQFDUFEFOEPGJOQVU 4ZOUBY&SSPS

8IZJTUIJTIBQQFOJOH 5IFQBSTJOHMPHTIPXTUIFSFBTPO

SVCZZFJJ 5IFQBSTJOHMPHTIPXTXIZ 1BSTJOHMPHTDBOCFFBTJMZPCUBJOFECZSVOOJOH UIFTDSJQUXJUIAZAPQUJPOUPUIFASVCZADPNNBOE TPMFUTHJWFJUBUSZXJUIBTDSJQUAJJ A 3VOUIFTDSJQU JJ
XJUIASVCZZADPNNBOE ˞5IJTJTSVOOJOHPO3VCZ

SVCZZFJJ BEE@EFMBZFE@UPLFO cc 4UBSUJOHQBSTF ʜ &OUFSJOHTUBUF 4UBDLOPX 3FEVDJOHTUBDLCZSVMF
MJOF OUFSNMIT /0%&@-"4(/ UPLFO OUFSNMFY@DUYU OUFSNBSH@SIT /0%&@-*5 OUFSNBSH /0%&@-"4(/ ʜ 5IFQBSTJOHMPHTIPXTXIZ "DDPSEJOHUPJU JUXPSLT fi OFVQUPAJA AJATFFNTUPCFQBSTFEKVTU fi OF

SVCZZFJJ ʜ &OUFSJOHTUBUF 4UBDLOPX /FYUUPLFOJTUPLFO 4IJGUJOHUPLFO
&OUFSJOHTUBUF 4UBDLOPX 3FEVDJOHTUBDLCZSVMF MJOF UPLFO OUFSNUFSN &OUFSJOHTUBUF 4UBDLOPX 3FEVDJOHTUBDLCZSVMF MJOF OUFSNUFSN OUFSNUFSNT 5IFQBSTJOHMPHTIPXTXIZ 5IFOUIF fi STUFYQSFTTJPOJTQSPQFSMZFOEFEXJUIAA 5IJTFYQSFTTJPOJTTVDDFTTGVMMZFOEFE AABMTPTFFNTUPCFQBSTFEDPSSFDUMZ

SVCZZFJJ ʜ &OUFSJOHTUBUF 4UBDLOPX 3FBEJOHBUPLFO QBSTFS@EJTQBUDI@TDBO@FWFOU cc MFY@TUBUF#&($.%"3(BUMJOF
MFY@TUBUF$.%"3(&/%c-"#&-BUMJOF QBSTFS@EJTQBUDI@TDBO@FWFOU cc /FYUUPLFOJTUPLFOMPDBMWBSJBCMFPSNFUIPE J 4IJGUJOHUPLFOMPDBMWBSJBCMFPSNFUIPE J 5IFQBSTJOHMPHTIPXTXIZ *OUIFMBUFSQBSU UIFWBSJBCMFAJAJT fi STUSFBE 5IFWBSJBCMFAJAJTSFBE

SVCZZFJJ ʜ &OUFSJOHTUBUF 4UBDLOPX /FYUUPLFOJTUPLFO 4IJGUJOHUPLFO
&OUFSJOHTUBUF 4UBDLOPX 3FBEJOHBUPLFO MFY@TUBUF#&(#&(BUMJOF QBSTFS@EJTQBUDI@TDBO@FWFOU cc /FYUUPLFOJTUPLFOVOBSZ 4IJGUJOHUPLFOVOBSZ 5IFQBSTJOHMPHTIPXTXIZ 5XPA ATBSFUIFOSFBE5IJT TFDPOEA AJT EFUFSNJOFEBTUIFA APGBVOBSZPQFSBUPS 'JSTUA A 4FDPOEA A *UTEFUFSNJOFEUIBUBVOBSZPQFSBUPS

SVCZZFJJ ʜ &OUFSJOHTUBUF 4UBDLOPX 3FBEJOHBUPLFO QBSTFS@EJTQBUDI@TDBO@FWFOU cc /PXBUFOEPGJOQVU
FTZOUBYFSSPS VOFYQFDUFEFOEPGJOQVU JJ 5IFQBSTJOHMPHTIPXTXIZ .3*FYQFDUTTPNFOVNFSJDUPCFSFBEBGUFS BVOBSZPQFSBUPSJOUIJTDPOUFYU )PXFWFS JOSFBMJUZ UIFMJOFFOETBCSVQUMZIFSF 5IJTJTBOVOFYQFDUFEFOEPGJOQVU "TZOUBYFSSPSIBTPDDVSSFE 5IFMJOFFOEFEVOFYQFDUFEMZ

5IJTJTXIZXFHFUBTZOUBYFSSPS XIFOXFUSZUPVTFA AJOUIFDVSSFOU.3*

#VUUIFO JGXFSFBMMZ SFBMMZXBOU PQFSBUPS IPXEPXFEPʜ

5BLFPOUIFDIBMMFOHFPGBEEJOH OFXTZOUBYJO3VCZ

4P JOUIJTUBML *XPVMEMJLFUPTIBSFXJUIQSPHSBNNFSTMJLFNF XIPJTOPUBQBSTFSFYQFSU XIBUJUUBLFTUPBEEOFXTZOUBYUP.3* CBTFEPONZEPDVNFOUBSZ

*OBEEJUJPO .3*TQBSTFSIBTCFFOBDUJWFMZEFWFMPQFEBOE TFWFSBMUBMLTXJMMCFHJWFOBUUIJTZFBST3VCZ,BJHJ 5IJTUBMLXJMMCFCBTFEPOUIFTPVSDFDPEFPG .3*XBTSFMFBTFEUIJT.BSDI

5PVSJOH.3*`TQBSTFS

/PX -FUTUBLFBRVJDLMPPL BUIPX.3*QBSTFT3VCZTDSJQUT CFGPSFXFUSZUPBEEBOFXTZOUBYUP3VCZ

"3VCZTDSJQUDPOTJTUTPGBTFRVFODFPGUPLFOT UIBUBSFWBMJEBT3VCZTZOUBY 5PLFOTDPOTUJUVUFB3VCZTDSJQU 5IJTTDSJQUDPOTJTUTPG QVUT )FMMP puts "Hello"

.3*SFBETUIFTFUPLFOTPOFCZPOF GSPNMFGUUPSJHIU VTJOHBGVODUJPODBMMFETDBOOFS )PXTDBOOFSXPSLT SFBETUIFUPLFOJT puts "Hello" QVUT 4DBOOFS
/PUF4DBOOFSJTBMTPDBMMFEMFYJDBMBOBMZ[FSPSMFYFS CVUKVTUDBMMJUTDBOOFSJOUIJTTMJEF

5IFTDBOOFSUIFOEFUFSNJOFTUIFLJOEPGUPLFOJUSFBET 5IFLJOEPGUPLFOJTDBMMFEBTZNCPM )PXTDBOOFSXPSLT EFUFSNJOFTUIFUPLFOQVUTJT U*%&/5*'*&3 puts "Hello" QVUT 5PLFO 4DBOOFS

5IFTDBOOFSTFUTUIFWBMVFPGUIFUPLFOUPBTZNCPM 5IJTWBMVFDBOCFBOJE BO3/PEF PSTPNFUIJOHFMTF )PXTDBOOFSXPSLT TFUTU*%&/5*'*&3UPBNFUIPEJE QVUT puts "Hello" U*%&/5*'*&3
QVUT 4ZNCPM 5PLFO /PUF4PNFUPLFOTIBWFOPWBMVF /PUF7BMVFJTDBMMFETFNBOUJDWBMVF CVUKVTUDBMMJUWBMVFJOUIJTTMJEF 4DBOOFS

'JOBMMZ UIFTDBOOFSSFUVSOTUIJTTZNCPMXJUIUIFWBMVF UPBGVODUJPODBMMFEBQBSTFS )PXTDBOOFSXPSLT puts "Hello" SFUVSOTUIFTZNCPMXJUIUIFWBMVFUPBQBSTFS U*%&/5*'*&3 QVUT QVUT
7BMVF 4ZNCPM 5PLFO 4DBOOFS

)PXQBSTFSXPSLT 5IFQBSTFSJTBGVODUJPOUIBUSFDFJWFTBTZNCPMGSPNUIF TDBOOFS DIFDLTTZOUBY DSFBUFT3/PEFT BOETPPO 5IFSFBSFNBOZHSBNNBSSVMFTEF fi OFEJOUIFQBSTFS QBSTFS
U*%&/5*'*&3 QVUT 7BMVF 4ZNCPM 3/PEF 7$"-- QVUT SFDFJWF DSFBUF .BOZHSBNNBSSVMFT

)PXQBSTFSXPSLT 5IFTZOUBYSVMFTMPPLMJLFUIJT )FSFUIFSJHIUBOEMFGUIBOETJEFTBSFEF fi OFE // An example of a
grammar rule operation : tIDENTIFIER | tCONSTANT | tFID ; 5IFMFGUIBOETJEF 5IFSJHIUIBOETJEF 5IFMFGUIBOETJEFEF fi OFTTZNCPMTUIBUNBLFTZNCPMTNPSFBCTUSBDU 5IFSJHIUIBOETJEFEF fi OFTUIFPSJHJOBMTZNCPMT

)PXQBSTFSXPSLT 4ZNCPMTBSFUVSOFEJOUPNPSFBCTUSBDUTZNCPM XIFOUIFZNBUDIUIFSJHIUIBOETJEFPGUIFTZOUBYSVMFT 5IJTDIBOHFJTDBMMFESFEVDUJPO // An example of a grammar
rule operation : tIDENTIFIER | tCONSTANT | tFID ; .PSFBCTUSBDUTZNCPM 0SJHJOBMTZNCPMTBSFUVSOFEJOUP NPSFBCTUSBDUTZNCPM

)PXQBSTFSXPSLT 5IFWBMVFTFUGPSUIFTZNCPMCFGPSFSFEVDUJPOXJMMCF DBSSJFEPWFSUPUIFTZNCPMBGUFSSFEVDUJPO 6OMFTTBOBDUJPOUIBUXJMMCFEJTDVTTFEMBUFSJTEF fi OFE // An example of
a grammar rule operation : tIDENTIFIER | tCONSTANT | tFID ; 5IFNFUIPEJEQVUT UIFWBMVFPGU*%&/5*'*&3 JT TFUUPPQFSBUJPOBGUFSSFEVDUJPO

)PXQBSTFSXPSLT "MUIPVHIPQUJPOBM XIBUUPCFQFSGPSNFEXIFOB SFEVDUJPOIBTPDDVSSFEDBOCFEF fi OFEJOBHSBNNBSSVMF 5IJTJTDBMMFEBTFNBOUJDBDUJPO /PUF4JNQMZDBMMJUBOBDUJPOJOUIJTTMJEF // An
example of a grammar rule fcall : operation { $$ = NEW_FCALL($1, 0, &@$); nd_set_line($$, p->tokline); } 5IJTBDUJPOJTFYFDVUFE XIFOPQFSBUJPOJTSFEVDFEUPGDBMM

)PXBQBSTFSXPSLT 8JUIJOUIFBDUJPO FBDIWBMVFPGTZNCPMTDBOCFBDDFTTFE "WBSJBCMF5IFOVNCFSPGUIFPSEFSPGUIFTZNCPMTCFGPSFSFEVDUJPO TUPSFTFBDIWBMVF "WBSJBCMFNFBOTUIFTZNCPMTWBMVFBGUFSSFEVDUJPO // An example
of a grammar rule fcall : operation { // $1 // $$ } 5IFWBMVFPGPQFSBUJPO5IFNFUIPEJEQVUT 5IFWBMVFPGGDBMM

)PXQBSTFSXPSLT *ONBOZDBTFT UIFBDUJPOEF fi OFTBQSPDFTTUPDSFBUFBO 3/PEFGSPNUIFWBMVFTFUJOUIFTZNCPMCFGPSFSFEVDUJPO 5IF3/PEFDSFBUFEJOUIJTXBZJTTFUUPUIFTZNCPMBGUFS SFEVDUJPO // An
example of a grammar rule fcall : operation { $$ = NEW_FCALL($1, 0, &@$); nd_set_line($$, p->tokline); } $SFBUFBO3/PEFGSPN BOETFUJUUP

)PXQBSTFSXPSLT 4PNFUJNFTUXPPSNPSFTZNCPMTBSFSFEVDFEBUPODF *OTVDIDBTFT HSBNNBSSVMFTWFSJGZUIBUUIFTFRVFODFPG TZNCPMTJTDPSSFDU *GUIFTFRVFODFPGTZNCPMTJTJODPSSFDU UIFSFEVDUJPOXJMM OPUCFFYFDVUFE BOEBTZOUBYFSSPSXJMMPDDVS //
An example of a grammar rule command : fcall command_args // ... 7FSJGZJOHGDBMMBOEDPNNBOE@BSHTBSF JOBSPXBOEPSEFSGSPNMFGUUPSJHIU

"MMPGUIFTZNCPMT HSBNNBSSVMFT BOEUIFTDBOOFSBSF EF fi OFEJOUIF fi MFQBSTFZJOUIF.3*TPVSDF SVCZQBSTFZ

/PX CBTFEPOUIJT -FUT fi HVSFPVUIPXUPJNQMFNFOUA AJO.3*

$BMMJOHBNFUIPEXJUIA A

5IF fi STUJEFBJT3FQMBDFA AXJUI*OUFHFSTVDD XIFOA AJTSFBEGSPNUIFTPVSDFDPEF i = 0
i++ # => Call Integer#succ and return 1 *OUFHFSTVDDSFUVSOTUIFWBMVFPGUIFSFTVMU XIJDIJTJODSFNFOUFECZUIFSFDFJWFS*OUFHFSPCKFDU i = 0 i.succ # => 1 $BMMJOHBNFUIPEXJUIA A A ABDUTMJLFBOBMJBTGPS*OUFHFSTVDDJOUIJTJEFB

5IFSFBSFUXPOFDFTTBSZUIJOHTUPJNQMFNFOUUIJT $BMMJOHBNFUIPEXJUIA A

5IFSFBSFUXPOFDFTTBSZUIJOHTUPJNQMFNFOUUIJT "OFXTZNCPMGPS 4ZNCPM i++ $BMMJOHBNFUIPEXJUIA A 5PLFO
%F fi OFBOFXTZNCPMGPSUIFUPLFO BOENBLFUIF TDBOOFSSFUVSOTUIFTZNCPMXIFOJUJTSFBE UPLFO

5IFSFBSFUXPOFDFTTBSZUIJOHTUPJNQMFNFOUUIJT "EEHSBNNBSSVMFTUPQBSTFBTDSJQUMJLFAJ A BOEDBMM*OUFHFSTVDDJOTJEFPGUIFBDUJPO -FUTHFUUPJU ⬇︎ i = 0 i++
# Call Integer#succ internally $BMMJOHBNFUIPEXJUIA A %F fi OFBOFXTZNCPMGPSUIFUPLFO BOENBLFUIF TDBOOFSSFUVSOTUIFTZNCPMXIFOJUJTSFBE UPLFO

// ruby/parse.y // ... %token <id> tIDENTIFIER "local variable or
method" %token <id> tFID "method" %token <id> tGVAR "global variable" %token <id> tIVAR "instance variable" %token <id> tCONSTANT "constant" %token <id> tCVAR "class variable" %token <id> tLABEL "label" %token <node> tINTEGER "integer literal" %token <node> tFLOAT "float literal" %token <node> tRATIONAL "rational literal" // ... %F fi OFBOFXTZNCPM *OQBSTFZ TZNCPMTBSFEF fi OFEMJLFUIJT

// ruby/parse.y // ... %token <id> tINCOP "increment operator" %token
<id> tIDENTIFIER "local variable or method" %token <id> tFID "method" %token <id> tGVAR "global variable" %token <id> tIVAR "instance variable" %token <id> tCONSTANT "constant" %token <id> tCVAR "class variable" %token <id> tLABEL "label" %token <node> tINTEGER "integer literal" %token <node> tFLOAT "float literal" %token <node> tRATIONAL "rational literal" // ... /PXMFU`TBEEBOFXTZNCPMU*/$01IFSF GPSUIFUPLFO %F fi OFBOFXTZNCPM %F fi OFBOFXTZNCPM

// ruby/parse.y static enum yytokentype parser_yylex(struct parser_params *p) { //
... .BLFUIFTDBOOFSSFUVSOU*/$01 5IFO NPEJGZUIFTDBOOFSUPSFUVSOU*/$01 XIFO JTSFBE *O.3* BGVODUJPOQBSTFS@ZZMFY EPFTNBOZPGXIBU BTDBOOFSEPFTGPSMFYJDBMBOBMZTJT

... switch (c = nextc(p)) { // ... .BLFUIFTDBOOFSSFUVSOU*/$01 5IFSFJTBIVHFTXJUDITUBUFNFOUJOJU 5IJTJTUPSFBEUIFDIBSBDUFSTJOUIFTDSJQUPOFBUB UJNFBOEEPTPNFUIJOHEFQFOEJOH POUIFDIBSBDUFSSFBE %PTPNFUIJOHEFQFOEJOHPOUIFDIBSBDUFSTSFBE

... switch (c = nextc(p)) { // ... case '+': // ... .BLFUIFTDBOOFSSFUVSOU*/$01 *OUIJTTXJUDITUBUFNFOU JUJTBMSFBEZEF fi OFE XIBUUPEPJGUIFDIBSBDUFSSFBEJT *GUIFDIBSBDUFSSFBEJT

... switch (c = nextc(p)) { // ... case '+': c = nextc(p); if (IS_AFTER_OPERATOR()) // ... if (c == '=') // ... .BLFUIFTDBOOFSSFUVSOU*/$01 *OJU BOBQQSPQSJBUFTZNCPMJTSFUVSOFEEFQFOEJOHPO UIFDIBSBDUFSCFGPSFBOEBGUFSUIF 3FBEUIFOFYUDIBSBDUFSPGUIF 3FUVSOTPNFUPLFOJGUIFQSFWJPVTDIBSBDUFSJT 3FUVSOTPNFUPLFOJGUIFOFYUDIBSBDUFSJT "OEPUIFS

... switch (c = nextc(p)) { // ... case '+': c = nextc(p); if (c == '+') .BLFUIFTDBOOFSSFUVSOU*/$01 -FUTBEEBOFXDPOEJUJPOIFSF *GUIFOFYUDIBSBDUFSBGUFS JT BHBJO 3FBEUIFOFYUDIBSBDUFSPGUIF *GUIFOFYUDIBSBDUFSJT BHBJO

... switch (c = nextc(p)) { // ... case '+': c = nextc(p); if (c == '+') { return tINCOP; } // ... .BLFUIFTDBOOFSSFUVSOU*/$01 SFUVSOU*/$01 UIFOFXTZNCPMEF fi OFEFBSMJFS 5IFTDBOOFSNPEJ fi DBUJPOJTOPXDPNQMFUF 3FBEUIFOFYUDIBSBDUFSPGUIF *GUIFOFYUDIBSBDUFSJT BHBJO 3FUVSOU*/$01

// ruby/parse.y method_call : fcall paren_args // ... | primary_value
call_op operation2 opt_paren_args // ... | primary_value tCOLON2 operation2 paren_args // ... | primary_value tCOLON2 operation3 // ... | primary_value call_op paren_args // ... %F fi OFBOFXHSBNNBSSVMF /FYU MFU`TEF fi OFBOFXHSBNNBSSVMFUPUIFQBSTFS GPSUIFTZOUBYMJLFAJ A QBSTFZEF fi OFTNBOZHSBNNBSSVMFTMJLFUIJTUP TVQQPSUWBSJPVTQBUUFSOTPGNFUIPEDBMMT

// ruby/parse.y method_call : fcall paren_args // ... | primary_value
call_op operation2 opt_paren_args // ... | primary_value tCOLON2 operation2 paren_args // ... | primary_value tCOLON2 operation3 // ... | primary_value call_op paren_args // ... | ???? %F fi OFBOFXHSBNNBSSVMF *UTFFNTBHPPEJEFBUPEF fi OFBOFXHSBNNBSSVMF IFSFGPSBNFUIPEDBMM %F fi OFBOFXHSBNNBSSVMF

// ruby/parse.y method_call : // ... | primary_value tINCOP %F
fi OFBOFXHSBNNBSSVMF )FSFJTUIFHSBNNBSSVMFUPCFBEEFE 5IFOFXHSBNNBSSVMFDIFDLTUIBUUIFTZNCPMT QSJNBSZ@WBMVFBOEU*/$01BSFJOBSPX %F fi OFBOFXHSBNNBSSVMF

// ruby/parse.y method_call : // ... | primary_value tINCOP QSJNBSZ@WBMVFJTUIFTZNCPMGPSUIFSFDFJWFSPGUIJT
FYQSFTTJPO BOEU*/$01JTGPSA A 5IJTNBLFTFYQSFTTJPOTMJLFAJ AWBMJEBTBTZOUBY 5IFTFTZNCPMTNFBOTʜ J # In a Ruby script i++ %F fi OFBOFXHSBNNBSSVMF

// ruby/parse.y method_call : // ... | primary_value tINCOP {
// ... %F fi OFBOFXBDUJPOUPDBMM*OUFHFSTVDD /FYU EF fi OFBOBDUJPO XIJDIDBMMT*OUFHFSTVDD XIFOSFEVDUJPOIBTPDDVSSFEGPSUIJTHSBNNBSSVMF

SET_LEX_STATE(EXPR_END); %F fi OFBOFXBDUJPOUPDBMM*OUFHFSTVDD 5IF fi STUXFOFFEUPEPJTUPUFMMUIFTDBOOFSUIBUUIJT FYQSFTTJPOFOETXIFO JTSFBE 5IJTJTOFFEFEUPQSFWFOUUIFTDBOOFSSFBETUIFOFYU UPLFOBGUFS BOEDBVTJOHBTZOUBYFSSPS5PEPTP DBMMUIFNBDSP4&5@-&9@45"5&XJUI&913@&/% 5FSNJOBUFUIJTFYQSFTTJPO /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF

SET_LEX_STATE(EXPR_END); ??? %F fi OFBOFXBDUJPOUPDBMM*OUFHFSTVDD /FYU MFUT fi OBMMZDBMM*OUFHFSTVDD )PXDBOXFEPUIBU /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF

// ruby/parse.y static NODE * new_qcall(struct parser_params* p, ID atype,
NODE *recv, ID mid, NODE *args, const YYLTYPE *op_loc, const YYLTYPE *loc) OFX@RDBMM .3*QSPWJEFTOFX@RDBMM UPDSFBUFBO3/PEF UPDBMMBNFUIPE -FUTVTFUIJTGVODUJPOUPEPXIBUJTUIFTBNF BTUIFNFUIPEDBMMJOUIFBDUJPO

// ruby/parse.y static NODE * new_qcall(struct parser_params* p, ID atype,
NODE *recv, ID mid, NODE *args, const YYLTYPE *op_loc, const YYLTYPE *loc) OFX@RDBMM 4PNFBSHVNFOUTBSFSFRVJSFEUPDBMMUIJTGVODUJPO "O3/PEFUIBUJTUIFSFDFJWFSPGUIFNFUIPE 5IFNFUIPEJE "O3/PEFUIBUJTUIFBSHVNFOUTPGUIFNFUIPE

SET_LEX_STATE(EXPR_END); new_qcall(p, $2, ???, ???, ???, &@2, &@$); $BMMOFX@RDBMM UPDBMM*OUFHFSTVDD 4PMFUTQSFQBSFUIFBSHVNFOUTUPDBMMOFX@RDBMM OFX@RDBMM OFFETBSHVNFOUT /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF

SET_LEX_STATE(EXPR_END); new_qcall(p, $2, ???, ???, ???, &@2, &@$); $BMMOFX@RDBMM UPDBMM*OUFHFSTVDD 'JSTU OFX@RDBMM OFFETBO3/PEFUIBUJTUIFSFDFJWFS BTUIFUIJSEBSHVNFOU "O3/PEFUIBUJTUIFSFDFJWFS /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF

// ruby/parse.y method_call : // ... | primary_value tINCOP $BMMOFX@RDBMM
UPDBMM*OUFHFSTVDD "TNFOUJPOFEFBSMJFS QSJNBSZ@WBMVFJTUIFTZNCPM UIBUJTUIFSFDFJWFSPGUIJTFYQSFTTJPO 5IJTTZNCPMIBTBO3/PEFPGUIFSFDFJWFSBTJUTWBMVF QSJNBSZ@WBMVF ʹUIFSFDFJWFS IBT BO3/PEFPGUIFSFDFJWFSPCKFDUBTJUTWBMVF /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF

// ... $1; $BMMOFX@RDBMM UPDBMM*OUFHFSTVDD 3FNFNCFS XFDBOHFUUIFTZNCPMTWBMVFXJUI BOVNCFSPGUIFPSEFSPGUIFTZNCPMT JOBOBDUJPO 5IFWBMVFPGQSJNBSZ@WBMVF JF UIF3/PEFUIBUJT UIFSFDFJWFSJTTUPSFEGPS 5IFWBMVFPGQSJNBSZ@WBMVF /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF

SET_LEX_STATE(EXPR_END); new_qcall(p, $2, $1, ???, ???, &@2, &@$); $BMMOFX@RDBMM UPDBMM*OUFHFSTVDD 4PDBOCFQBTTFEBTJTBTUIFUIJSEBSHVNFOUPG OFX@RDBMM /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF 5IFWBMVFPGQSJNBSZ@WBMVF 5IF3/PEFUIBUJTUIFSFDFJWFS

$BMMOFX@RDBMM UPDBMM*OUFHFSTVDD // ruby/parse.y method_call : // ... | primary_value
tINCOP { SET_LEX_STATE(EXPR_END); new_qcall(p, $2, $1, ???, ???, &@2, &@$); /FYU UIFGPVSUIBSHVNFOUPGOFX@RDBMM JT BNFUIPEJEPGUIFDBMMJOHNFUIPE /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF 5IFNFUIPEJE

$BMMOFX@RDBMM UPDBMM*OUFHFSTVDD // ruby/parse.y method_call : // ... | primary_value
tINCOP { SET_LEX_STATE(EXPR_END); ID succ = rb_intern("succ"); new_qcall(p, $2, $1, succ, ???, &@2, &@$); (FUUIFNFUIPEJEPG*OUFHFSTVDDBOEQBTTJU UPOFX@RDBMM (FUUIFNFUIPEJEPG*OUFHFSTVDD /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF 1BTTUIFNFUIPEJE

SET_LEX_STATE(EXPR_END); ID succ = rb_intern("succ"); new_qcall(p, $2, $1, succ, ???, &@2, &@$); // ... } $BMMOFX@RDBMM UPDBMM*OUFHFSTVDD 5IF fi GUIBSHVNFOUJTBO3/PEFXIJDIJT UIFDBMMJOHNFUIPEBSHVNFOU /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF 5IFBSHVNFOUTPGUIFDBMMJOHNFUIPE

SET_LEX_STATE(EXPR_END); ID succ = rb_intern("succ"); new_qcall(p, $2, $1, succ, Qnull, &@2, &@$); // ... } $BMMOFX@RDBMM UPDBMM*OUFHFSTVDD )PXFWFS *OUFHFSTVDDOPBSHVNFOU -FUTQBTTOJMIFSF /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF 1BTTOJM

SET_LEX_STATE(EXPR_END); ID succ = rb_intern("succ"); $$ = new_qcall(p, $2, $1, succ, Qnull, &@2, &@$); $BMMOFX@RDBMM UPDBMM*OUFHFSTVDD 'JOBMMZ TFUUIF3/PEFPGUIFNFUIPEDBMM UIFSFUVSO WBMVFPGOFX@RDBMM UPUIFTZNCPMBGUFSSFEVDUJPO 5IJTDPNQMFUFTUIFWJUBMQBSUPGUIFJNQMFNFOUBUJPO "TTJHOUIFSFUVSOWBMVFUPUIFTZNCPMBGUFSSFEVDUJPO /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF

*TJUXPSLJOH NBLFSVO 3VOUIFDPNQJMFDPNNBOE # ruby/test.rb i = 0 i++ 8JUIUIJTJNQMFNFOUBUJPO
XSJUFBTDSJQUDPOUBJOJOH A A UIFOSVOUIFDPNQJMFDPNNBOE

*UMPPLTXPSLJOH NBLFSVO HFOFSBUJOHQBSTFD DPNQJMJOHQBSTFD MJOLJOHNJOJSVCZ NJOJSVCZ*SVCZMJC*a *FYUDPNNPOa SBSNEBSXJOGBLF SVCZUFTUSC
# ruby/test.rb i = 0 i++ *USFUVSOTBOJODSFNFOUFEWBMVFXJUIPVUBOZ TZOUBYFSSPS 5IFJNQMFNFOUBUJPOPG JTTVDDFTTGVM *USFUVSOTJODSFNFOUFEWBMVF

)PXFWFSʜ

*GPVOEBQSPCMFNXJUIUIJTJNQMFNFOUBUJPO i = 0 i++ # => It returns 1
i # => But i is still 0... *UJTUIBU*OUFHFSTVDDEPFTOPUBTTJHOJUTSFUVSOWBMVF UPUIFSFDFJWFSWBSJBCMF

0, MFU`TUIJOLPGBOPUIFSXBZ

$BMMJOHBNFUIPEXJUIA A SFWJTFE

*OUIFQSFWJPVTJNQMFNFOUBUJPO UIFSFJTBQSPCMFNUIBU*OUFHFSTVDDEJEOPUBTTJHO UIFSFUVSOWBMVFUPUIFSFDFJWFS i = 0 i++ # =>
Call Integer#succ, then i is still 0 4P JOTUFBEPG*OUFHFSTVDD MFUTDBMMTPNFPUIFS UIBUDBOBTTJHOUIFJODSFNFOUFEWBMVFUPUIFSFDFJWFS i = 0 i++ # => Call some other method, then i becomes 1 $BMMJOHBNFUIPEXJUIA A SFWJTFE NFUIPE

5IFSFBSFUXPOFDFTTBSZUIJOHTUPJNQMFNFOUUIJT $BMMJOHBNFUIPEXJUIA A SFWJTFE

5IFSFBSFUXPOFDFTTBSZUIJOHTUPJNQMFNFOUUIJT "EEBOFXNFUIPE*OUFHFS@@QMVTQMVT@@UPBTTJHO BOJODSFNFOUFEWBMVFUPUIFSFDFJWFS i = 0 i.__plusplus__ p i #
=> 1 $BMMJOHBNFUIPEXJUIA A SFWJTFE

5IFSFBSFUXPOFDFTTBSZUIJOHTUPJNQMFNFOUUIJT "EEBOFXNFUIPE*OUFHFS@@QMVTQMVT@@UPBTTJHO BOJODSFNFOUFEWBMVFUPUIFSFDFJWFS $BMM*OUFHFS@@QMVTQMVT@@JOTUFBEPG*OUFHFSTVDD JOUIFBDUJPO -FUTHFUUPJU ⬇︎ i =
0 i++ # Call i.__plusplus__ internally $BMMJOHBNFUIPEXJUIA A SFWJTFE

# ruby/numeric.rb class Integer def __plusplus__(name, b) b.local_variable_set(name, self.succ) end
# ... %F fi OF*OUFHFS@@QMVTQMVT@@ ,FSOFMMPDBM@WBSJBCMF@TFUPSTPNFUIJOH %FUFSNJOFUIFUZQFPGUIFWBSJBCMFGSPNUIFWBSJBCMFOBNF 1BTTUIFBSHVNFOUT ɾWBSJBCMFOBNF ɾB#JOEJOHPCKFDU 'JSTU MFU`TEF fi OF*OUFHFS@@QMVTQMVT@@ *UJODSFNFOUTTFMGBOETFUTJUTWBMVFUPBWBSJBCMF JOJUTFOWJSPONFOUVTJOHUIFBSHVNFOUT

# ruby/numeric.rb class Integer def __plusplus__(name, b) b.local_variable_set(name, self.succ) end
# ... %F fi OF*OUFHFS@@QMVTQMVT@@ *OUFHFS@@QMVTQMVT@@DBOCFDBMMFEMJLFUIJT JOB3VCZTDSJQU *UBTTJHOTBOJODSFNFOUFEWBMVFUPUIFSFDFJWFS # In a Ruby script i = 0 i.__plusplus__("i", binding) i # => 1 1BTTUIFBSHVNFOUT ɾWBSJBCMFOBNF ɾ,FSOFMCJOEJOH

SET_LEX_STATE(EXPR_END); ID succ = rb_intern("succ"); $$ = new_qcall(p, $2, $1, succ, Qnull, &@2, &@$); // ... } .PEJGZUIFBDUJPOUPDBMM*OUFHFS@@QMVTQMVT@@ /FYU MFU`TNPEJGZUIFBDUJPOUPDBMM *OUFHFS@@QMVTQMVT@@JOTUFBEPG*OUFHFSTVDD *OUFHFSTVDDJTDBMMFEJOUIFQSFWJPVTJNQMFNFOUBUJPO /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF

SET_LEX_STATE(EXPR_END); // ... $$ = new_qcall(p, $2, $1, ???, ???, &@3, &@$); .PEJGZUIFBDUJPOUPDBMM*OUFHFS@@QMVTQMVT@@ 'JSTU JOUIFTBNFXBZBTCFGPSF DBMMUIF4&5@-&9@45"5&NBDSPBOEQBTT BTUIFUIJSEBSHVNFOUUPOFX@RDBMM 5FSNJOBUFUIJTFYQSFTTJPO /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF 1BTTUIFWBMVFPGUIFSFDFJWFS

SET_LEX_STATE(EXPR_END); ID plusplus = rb_intern("__plusplus__"); $$ = new_qcall(p, $2, $1, plusplus, ???, &@3, &@$); .PEJGZUIFBDUJPOUPDBMM*OUFHFS@@QMVTQMVT@@ 1BTTUIFNFUIPEJEPG*OUFHFS@@QMVTQMVT@@ BTUIFGPVSUIBSHVNFOU /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF 1BTTUIFNFUIPEJE (FUUIFNFUIPEJEPG*OUFHFS@@QMVTQMVT@@

SET_LEX_STATE(EXPR_END); ID plusplus = rb_intern("__plusplus__"); $$ = new_qcall(p, $2, $1, plusplus, ???, &@3, &@$); .PEJGZUIFBDUJPOUPDBMM*OUFHFS@@QMVTQMVT@@ /PX *OUFHFS@@QMVTQMVT@@SFRVJSFTUXPBSHVNFOUT /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF # In a Ruby script i = 0 i.__plusplus__("i", binding)

SET_LEX_STATE(EXPR_END); ID plusplus = rb_intern("__plusplus__"); $$ = new_qcall(p, $2, $1, plusplus, ???, &@3, &@$); .PEJGZUIFBDUJPOUPDBMM*OUFHFS@@QMVTQMVT@@ 5IF fi STUJTBTUSJOHMJUFSBMPGUIFWBSJBCMFOBNF BOEUIFTFDPOEJTBNFUIPEDBMMPG,FSOFMCJOEJOH /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF # In a Ruby script i = 0 i.__plusplus__("i", binding) 1BTTUIFBSHVNFOUT ɾWBSJBCMFOBNF ɾ,FSOFMCJOEJOH

SET_LEX_STATE(EXPR_END); ID plusplus = rb_intern("__plusplus__"); $$ = new_qcall(p, $2, $1, plusplus, ???, &@3, &@$); .PEJGZUIFBDUJPOUPDBMM*OUFHFS@@QMVTQMVT@@ 5IFTFBSHVNFOUTNVTUCFQSFQBSFEBTBO3/PEF UIBUJTBOBSSBZBOEUIFOQBTTFEUPUIF fi GUIBSHVNFOU PGOFX@RDBMM 1BTTUIFBSHVNFOUTIFSF BTBO3/PEFUIBUJTBOBSSBZ /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF

// $1; // $1->u1.id; .PEJGZUIFBDUJPOUPDBMM*OUFHFS@@QMVTQMVT@@ 4P MFUTDSFBUFUIFTUSJOHMJUFSBMPGUIFSFDFJWFS`T WBSJBCMFOBNF 8FDBOHFUUIF3/PEFPGUIFSFDFJWFSGSPN 5IFWBSJBCMFJEJTTUPSFEJOBNFNCFSPGUIJT3/PEF /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF 5IFWBMVFPGQSJNBSZ@WBMVF 5IF3/PEFPGUIFSFDFJWFSPCKFDU 5IFWBSJBCMFJEPGUIFSFDFJWFS

// ... VALUE v = QUOTE_ID($1->u1.id); NODE *receiver = NEW_LIT(v, &NULL_LOC); .PEJGZUIFBDUJPOUPDBMM*OUFHFS@@QMVTQMVT@@ $SFBUFB7"-6&PG4USJOHGSPNUIFWBSJBCMFJE BOEDSFBUFBO3/PEFPGBMJUFSBMGSPNUIJTWBMVF *UDBOCFUIF fi STUBSHVNFOUPG*OUFHFS@@QMVTQMVT@@ "O3/PEFUIBUJTBTUSJOHMJUFSBMGSPNUIF7"-6& 7"-6&PGUIFTUSJOHGSPNUIFWBSJBCMFJE /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF

// ... VALUE v = QUOTE_ID($1->u1.id); NODE *receiver = NEW_LIT(v, &NULL_LOC); NODE *binding = NEW_VCALL(rb_intern("binding"), &@$); .PEJGZUIFBDUJPOUPDBMM*OUFHFS@@QMVTQMVT@@ /FYU DSFBUFBO3/PEFUIBUDBMMT,FSOFCJOEJOH BTUIFTFDPOEBSHVNFOUPG*OUFHFS@@QMVTQMVT@@ "O3/PEFUIBUDBMMT,FSOFMCJOEJOH /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF

// ... VALUE v = QUOTE_ID($1->u1.id); NODE *receiver = NEW_LIT(v, &NULL_LOC); NODE *binding = NEW_VCALL(rb_intern("binding"), &@$); NODE *args = NEW_LIST(receiver, &NULL_LOC); args = list_append(p, args, binding); .PEJGZUIFBDUJPOUPDBMM*OUFHFS@@QMVTQMVT@@ $SFBUFBO3/PEFUIBUJTBOBSSBZGSPNBO3/PEF PGUIFMJUFSBMBOEBO3/PEFPGUIFNFUIPEDBMM "O3/PEFUIBUJTBOBSSBZPGUIFBSHVNFOUT /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF

// ... VALUE v = QUOTE_ID($1->u1.id); NODE *receiver = NEW_LIT(v, &NULL_LOC); NODE *binding = NEW_VCALL(rb_intern("binding"), &@$); NODE *args = NEW_LIST(receiver, &NULL_LOC); args = list_append(p, args, binding); ID plusplus = rb_intern("__plusplus__"); $$ = new_qcall(p, $2, $1, plusplus, args, &@2, &@$); .PEJGZUIFBDUJPOUPDBMM*OUFHFS@@QMVTQMVT@@ 5IFOQBTTJUUPOFX@RDBMM BTJUT fi GUIBSHVNFOU 5IJTDPNQMFUFTUIFWJUBMQBSUPGUIFJNQMFNFOUBUJPO /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF

*TJUXPSLJOH 8JUIUIJTJNQMFNFOUBUJPO XSJUFBTDSJQUDPOUBJOJOH A ABOEDIFDLJOHUIFWBMVFPGUIFSFDFJWFS UIFOFYFDVUFTUIFDPNQJMFDPNNBOE NBLFSVO 3VOUIFDPNQJMFDPNNBOE #
ruby/test.rb i = 0 i++ p i

# ruby/test.rb i = 0 i++ p i JJTOPXJODSFNFOUFE 5IFOUIFDPNQJMBUJPOTVDDFFEFE BOEUIFWBSJBCMFXBT BTTJHOFEBOJODSFNFOUFEWBMVF 5IFJNQMFNFOUBUJPOPG JTTVDDFTTGVM

)PXFWFSʜ

*GPVOEBQSPCMFNJOUIJTJNQMFNFOUBUJPOBHBJO 1++ # => ??? *OUIJTJNQMFNFOUBUJPO A ABDUTMJLFBOBMJBTGPS*OUFHFS@@QMVTQMVT@@ *UNBLFTVTXBOUUPDBMMA
AFWFOJGUIFSFDFJWFSJTOPU BWBSJBCMFCVUBO*OUFHFSMJUFSBM )PXFWFS EPJOHTPXPVME

DBVTFBTFHNFOUBUJPOGBVMU

5IFSFDFJWFSJTOPUBMXBZTBWBSJBCMF // ruby/parse.y method_call : // ... | primary_value tINCOP
{ // ... SET_LEX_STATE(EXPR_END); VALUE v = QUOTE_ID($1->u1.id); 5IFSFBTPOJTUIBUUIJTJNQMFNFOUBUJPOOFFET UIFWBSJBCMFJEPGUIFSFDFJWFS 8FUSZUPHFUUIFWBSJBCMFJEVOEFSUIFBTTVNQUJPO UIBUUIF3/PEFPGUIFSFDFJWFSPCKFDUIBTJU &YQFDUJOHJTBO3/PEF UIBUIBTUIFWBSJBCMFJE /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF

// ... SET_LEX_STATE(EXPR_END); VALUE v = QUOTE_ID($1->u1.id); )PXFWFS JGUIFSFDFJWFSJTBMJUFSBM UIJT3/PEFEPFTOU IBWFUIFWBSJBCMFJE *OUIBUDBTF BOVOJOUFOEFENFNPSZBSFBJTBDDFTTFE BOEBTFHNFOUBUJPOGBVMUPDDVST 6OMFTTUIFSFDFJWFSJTBWBSJBCMF XFDBO`UBDDFTTWBSJBCMFJE /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF 5IFSFDFJWFSJTOPUBMXBZTBWBSJBCMF

3VCZIBTOPWBSJBCMFPCKFDU *UNFBOTUIBUXFJNQMJDJUMZFYQFDUUIFSFDFJWFSUPCFBWBSJBCMF XIFOXFXPVMEMJLFUPVTFA A "OEUIJTTFFNTUPCFXIBU.BU[TBZTUIBUDBO`UEFGJOFPCKFDU PSJFOUFETFNBOUJDTGPSJODSFNFOUEFDSFNFOUPQFSBUPST 8IJMFA AJTGPSNBOJQVMBUJOHWBSJBCMFT UIFSFBSFOPWBSJBCMF PCKFDUTJO3VCZUIBUDBOCFNBOJQVMBUFECZNFUIPET

4P MFUTTUPQDBMMJOHTPNFNFUIPEXJUIA A BOEUIJOLPGBOPUIFSXBZ

5VSOA AJOUPA A

4PGBS XFIBWFUSJFEUPDPOTJEFSA ABTBOBMJBTPG NFUIPEDBMM i++ )PXFWFS JOUIBUXBZ XFIBWFUPDPOTJEFSXIFUIFSUIF SFDFJWFSJTBWBSJBCMFPSBMJUFSBM BOEJUJTEJ
ff i DVMUUPCF DPOTJTUFOUXJUIJO3VCZTTFNBOUJDT 5VSOA AJOUPA A "NFUIPEDBMM

-FU`TGPSHFUBCPVUQSFWJPVTJEFBTBOE UIJOLNPSFTJNQMZ 8IBUXFXBOUUPEPJTA A 5VSOA AJOUPA A

4P XIZOPUKVTUDSFBUFUIFTBNF"45XJUIA A $ ruby -e "pp RubyVM::AbstractSyntaxTree.parse('i+= 1')" (SCOPE@1:0-1:5
tbl: [:i] args: nil body: (LASGN@1:0-1:5 :i (CALL@1:0-1:5 (LVAR@1:0-1:1 :i) :+ (LIST@1:4-1:5 (LIT@1:4-1:5 1) nil)))) 5VSOA AJOUPA A 5IF"45PGAJ A

*OQBSTFZ BHSBNNBSSVMFJTEF fi OFEUPQBSTFTDSJQUT TVDIBTAJ A i++ i += 1
4PJGXFDBOEPFYBDUMZUIFTBNFUIJOHBTAJ A XIFOUIFTDBOOFSSFBEBTDSJQUMJLFAJ A XF`MMCFBCMFUPQBSTFJUBTAJ A MJLFBTZOUBYTVHBS 5VSOA AJOUPA A ⬇︎

8IFOUIFTDBOOFSSFBETA A JUSFUVSOTUIFTZNCPM U01@"4(/GPSA ABOEU*/5&(&3GPSAA i += 1 i++ 3FUVSOUIFTBNFTZNCPMTBTA
A U01@"4(/ U01@"4(/ U*/5&(&3 3/PEF 4ZNCPM 7BMVF U*/5&(&3 3/PEF 4PJUXPVMECFOJDFJGUIFTDBOOFSDPVMESFUVSOCPUIU01@"4(/ BOEU*/5&(&3BUPODFXIFOJUSFBETA A CVUVOGPSUVOBUFMZ UIFTDBOOFSPOMZSFUVSOTPOFTZNCPMQFSSFBE

4PIPXBCPVUNPEJGZJOHUIFTDBOOFSMJLFUIJT i += 1 i++ 3FUVSOUIFTBNFTZNCPMTBTA A U01@"4(/ U01@"4(/
U*/5&(&3 3/PEF 4ZNCPM 7BMVF U*/5&(&3 3/PEF 'PSUIF fi STUA A SFUVSOUIFTZNCPMBOEWBMVFPGA A 'PSUIFTFDPOEA A SFUVSOUIFTZNCPMBOEWBMVFPGJOUFHFS

5IBOLGVMMZ .3*TDBOOFSIBTMPDBUJPOBMJOGPSNBUJPOJOUIF SFBEJOHMJOF5IFZDPVMECFIFMQGVMJOUIJTUJNF // ruby/parse.y /* Structure of Lexer Buffer:
lex.pbeg lex.ptok lex.pcur lex.pend | | | | |------------+------------+------------| |<---------->| token */ 5PQQPTJUJPOPGUIFMJOFSFBE &OEQPTJUJPOPGUIFMJOFSFBE $VSSFOUQPTJUJPOPGDVSTPS 5IFTDBOOFSIBTMPDBUJPOBMJOGPSNBUJPO

)FSFJTIPXUIFTDBOOFSTIPVMEXPSLXJUIUIJTJEFB i++ 8IFOUIFSFJTBTDSJQUMJLFAJ A UIFTDBOOFS fi STUSFBETJBTBWBSJBCMFAJABOE SFUVSOTUIFTZNCPMPGJU 5IFDVSTPSPGUIFTDBOOFSJTIFSF
8IBUUIFNPEJ fi FETDBOOFSEPFT 3FBEBOESFUVSOUIFTZNCPMPGUIFWBSJBCMFJ

i++ 5IFOUIFDVSTPSNPWFTPOFDIBSBDUFSBOEUIFTDBOOFS UIFOSFBETUIFOFYUDIBSBDUFS 4PGBS UIJTJTUIFDPOWFOUJPOBMCFIBWJPS 5IFDVSTPSJTIFSF 8IBUUIFNPEJ fi FETDBOOFSEPFT

i++ 5IFOFYUDIBSBDUFSJTUIF fi STU 8IFOUIFTDBOOFSSFBET EPOPUSFUVSOUIFTZNCPM JNNFEJBUFMZ CVUQFFLOFYUDIBSBDUFS
LFFQJOHUIFDVSTPS QPTJUJPO 8IBUUIFNPEJ fi FETDBOOFSEPFT 5IFDVSTPSJTIFSF 5IJTJT

i++ *GUIFOFYUDIBSBDUFSJTBMTP UIFTDBOOFSDBOTFFUIBUUIJTJTQBSUPGA A 5IFDVSTPSJTIFSF 5IJTJTBMTP 5IJTJT
8IBUUIFNPEJ fi FETDBOOFSEPFT

i++ 5IFTDBOOFSTIPVMEOPXSFUVSOU01@"4(/ UIFTZNCPMGPSUIFUPLFOA A 3FUVSOTU01@"4(/ 5IFDVSTPSJTIFSF 8IBUUIFNPEJ fi FETDBOOFSEPFT

i++ 5IFDVSTPSNPWFTPOFDIBSBDUFS UIFOUIFTDBOOFSSFBET UIFMBTUDIBSBDUFS 5IFMBTUDIBSBDUFSJTUIFTFDPOE 5IFDVSTPSJTIFSF 5IJTJT BHBJO 8IBUUIFNPEJ
fi FETDBOOFSEPFT

i++ 8IFOUIFTDBOOFSSFBETUIFTFDPOE QFFLBUUIFDIBSBDUFSJOUIFPOFQPTJUJPOCFGPSFJU LFFQJOHUIFDVSTPSQPTJUJPO 5IFDVSTPSJTIFSF 5IJTJT BHBJO

i++ *GUIFQSFWJPVTDIBSBDUFSJTBMTP UIFTDBOOFSDBOTFFUIBUUIJTJTQBSUPGA ABHBJO 5IJTJT BHBJO 5IFDVSTPSJTIFSF 5IJTJTBMTP

i++ 5IFOUIFTDBOOFSSFUVSOTU*/5&(&3 UIFTZNCPMPGBOJOUFHFS XJUIUIFWBMVFJOUFHFSTFU )PXDBOXFEP 3FUVSOUIFJOUFHFS 8IBUUIFNPEJ fi FETDBOOFSEPFT

// ruby/parse.y static eunm yytokentype set_integer_literal(struct parser_params *p, VALUE v,
int suffix) TFU@JOUFHFS@MJUFSBM .3*QSPWJEFTTFU@JOUFHFS@MJUFSBM *UDSFBUFTBO3/PEFUIBUJTBOJOUFHFSMJUFSBMBOE SFUVSOTUIFTZNCPMU*/5&(&3TFUXJUIJU

i++ $BMMJOHUIJTGVODUJPOXIFOUIFTFDPOE JTSFBEXJMM SFUVSOBTZNCPMXJUIBWBMVFPGJOUFHFS 5IJTXJMMDBVTFUIFTDBOOFSUPCFIBWFUIFTBNF BTXIFOJUSFBETA A-FUTHFUUPJU $BMMTFU@JOUFHFS@MJUFSBM $BMMTFU@JOUFHFS@MJUFSBM UPSFUVSOU*/5&(&3

... switch (c = nextc(p)) { // ... case '+': // ... .BLFUIFTDBOOFSSFUVSOU01@"4(/GPSUIF fi STU "TXFTBXFBSMJFS QBSTFS@ZZMFY UIBUFYFDVUFTMFYJDBM BOBMZTJTIBTBTXJUDITUBUFNFOUUPCFEF fi OFEBT XIBUUPEPJGUIFSFBEDIBSBDUFSJT -FUTNPEJGZJU *GUIFDIBSBDUFSSFBEJT i++

... switch (c = nextc(p)) { // ... case '+': peekc(p); .BLFUIFTDBOOFSSFUVSOU01@"4(/GPSUIF fi STU 'JSTU XIFOUIFTDBOOFSSFBET LFFQUIFDVSTPS QPTJUJPOBOEQFFLUIFOFYUDIBSBDUFSBGUFSJU 5IFSFJTBGVODUJPOQFFLD GPSJUJO.3* 1FFLUIFOFYUDIBSBDUFSPG i++

... switch (c = nextc(p)) { // ... case '+': if (peekc(p) == '+') { set_yylval_id('+'); SET_LEX_STATE(EXPR_BEG); return tOP_ASGN; } .BLFUIFTDBOOFSSFUVSOU01@"4(/GPSUIF fi STU *GUIFOFYUDIBSBDUFSJT SFUVSOUIFTZNCPM U01@"4(/XIJDINFBOTA A 3FUVSOU01@"4(/ *GUIFOFYUDIBSBDUFSJT i++ U01@"4(/

... switch (c = nextc(p)) { // ... case '+': if (peekc(p) == '+') { set_yylval_id('+'); SET_LEX_STATE(EXPR_BEG); return tOP_ASGN; } .BLFUIFTDBOOFSSFUVSOU01@"4(/GPSUIF fi STU 5IFOUIFDVSTPSNPWFTBIFBEUPPOFDIBSBDUFSBOE QBSTFS@ZZMFY BUUFNQUTUPSFBEUIFOFYUDIBSBDUFS 5IFDVSTPSNPWFTBIFBE i++

... switch (c = nextc(p)) { // ... case '+': if (peekc(p) == '+') { // ... } peekc_n(p, -2) .BLFUIFTDBOOFSSFUVSOU*/5&(&3GPSUIFTFDPOE /FYU XIFOUIFTDBOOFSSFBETUIFTFDPOE LFFQUIF DVSTPSQPTJUJPOBOEDIFDLUIFDIBSBDUFSPOFCFGPSFJU QFFLD@O QSPWJEFECZ.3*DBOCFVTFEGPSUIJT 1FFLUIFQSFWJPVTDIBSBDUFSPG *GUIFDIBSBDUFSSFBEJT i++

... switch (c = nextc(p)) { // ... case '+': if (peekc(p) == '+') { // ... } if (peekc_n(p, -2) == '+') { VALUE i = rb_cstr_to_inum("1", 16, FALSE); .BLFUIFTDBOOFSSFUVSOU*/5&(&3GPSUIFTFDPOE *GUIFQSFWJPVTDIBSBDUFSXBTBMTPB UIFODSFBUFB7"-6&UIBUJTBOJOUFHFS $SFBUFB7"-6&UIBUJTBJOUFHFS *GUIFQSFWJPVTDIBSBDUFSJT

... switch (c = nextc(p)) { // ... case '+': if (peekc(p) == '+') { set_yylval_id('+'); SET_LEX_STATE(EXPR_BEG); return tOP_ASGN; } if (peekc_n(p, -2) == '+') { VALUE i = rb_cstr_to_inum("1", 16, FALSE); return set_integer_literal(p, i, 0); } // ... .BLFUIFTDBOOFSSFUVSOU*/5&(&3GPSUIFTFDPOE 3FUVSOUIFSFTVMUPGTFU@JOUFHFS@MJUFSBM i++ U*/5&(&3 1BTTJUBTBOBSHVNFOUUPDBMMTFU@JOUFHFS@MJUFSBM BOESFUVSOUIFSFTVMUGSPNUIFTDBOOFS

... switch (c = nextc(p)) { // ... case '+': if (peekc(p) == '+') { set_yylval_id('+'); SET_LEX_STATE(EXPR_BEG); return tOP_ASGN; } if (peekc_n(p, -2) == '+') { VALUE i = rb_cstr_to_inum("1", 16, FALSE); return set_integer_literal(p, i, 0); } // ... .BLFUIFTDBOOFSSFUVSOU*/5&(&3GPSUIFTFDPOE 5IJTTIPVMESFUVSOUIFTBNFSFTVMUBTJGA A IBECFFOSFBE"OEUIJTJNQMFNFOUBUJPOJTDPNQMFUF U01@"4(/ U*/5&(&3 i++

*TJUXPSLJOH NBLFSVO # ruby/test.rb i = 0 i++ p i
3VOUIFDPNQJMFDPNNBOE 8JUIUIJTJNQMFNFOUBUJPO XSJUFBTDSJQUDPOUBJOJOH A ABOEDIFDLJOHUIFWBMVFPGUIFSFDFJWFS UIFOFYFDVUFTUIFDPNQJMFDPNNBOE

# ruby/test.rb i = 0 i++ p i JJTOPXJODSFNFOUFE 5IFOUIFDPNQJMBUJPOTVDDFFEFE BOEUIFWBSJBCMFXBT BTTJHOFEBOJODSFNFOUFEWBMVF

NBLFSVO NJOJSVCZ*SVCZMJC*a *FYUDPNNPOa SBSNEBSXJOGBLF SVCZUFTUSCSVCZUFTUSC TZOUBYFSSPS VOFYQFDUFEPQFSBUPSBTTJHONFOU FYQFDUJOHFOEPGJOQVU
4ZOUBY&SSPS NBLF <SVO>&SSPS *UMPPLTXPSLJOH # ruby/test.rb 1++ "OTZOUBYFSSPSIBTPDDVSSFE $BMMJOHA AXJUIBOJOUFHFSMJUFSBMEPFTOPUDBVTF BTFHNFOUBUJPOGBVMU CVUBTZOUBYFSSPSBTTBNFBT A A5IJTJTUIFJOUFOEFECFIBWJPS 5IFJNQMFNFOUBUJPOPG JTTVDDFTTGVM

)PXFWFSʜ

*GPVOEBQSPCMFNJOUIJTJNQMFNFOUBUJPOBHBJO i = 0 i++ * 2 # => 2
p i # => ? 8IFOFYFDVUJOHBTDSJQUMJLFUIJT XIBUXPVMECFBOBQQSPQSJBUFWBMVFGPSUIFWBSJBCMFAJA

5IJTJTBLJOEPGMBOHVBHFEFTJHONBUUFS BOEUIFSFBSF NBOZXBZTUPUIJOLBCPVUJU1FSTPOBMMZ *UIJOLJUJT BQQSPQSJBUFGPSUIFWBSJBCMFAJAUPCFBTTJHOFE i = 0 i++ *
2 # => Expect: (i += 1) * 2 p i # => Expect: 1 *FYQFDUUIFWBSJBCMFAJAUPCFBTTJHOFE fi STUBOE NVMUJQMJFECZOFYU

)PXFWFS UIJTA AJTFRVJWBMFOUUPA A5IFSFGPSF UIFSFTVMUJTBTTJHOFEUPUIFWBSJBCMFAJABGUFSUIF NVMUJQMJDBUJPOPG JTDPNQVUFE fi STUCZQSFDFEFODF
i = 0 i++ * 2 # => Actual: i += (1 * 2) p i # => Actual: 2 5IFOUIFWBSJBCMFAJAJTBTTJHOFE *GFFMUIJTJTBOBUVSBMCFIBWJPSGPSA A CVUBCJU TUSBOHFGPSA A

4JODFUIFQSFDFEFODFPGPQFSBUPSTJTEF fi OFEJOQBSTFZ JUJTQPTTJCMFUPBWPJEUIJTQSPCMFNCZNBLJOHUIF QSFDFEFODFPGA AIJHIFSUIBOA A // ruby/parse.y
// ... %right '=' tOP_ASGN %left modifier_rescue %right '?' ':' // ... %left '&' %left tLSHFT tRSHFT %left '+' '-' %left '*' '/' ‘%' // ... 5IFQSFDFEFODF )JHIFS -PXFS

)PXFWFS UIFQSPCMFNUIJTUJNFJTPOMZGPSUIFDBTFPG SFBEJOHA A*EPOUXBOUUPDIBOHFUIFQSFDFEFODFGPS UIFDBTFPGSFBEJOHA AVTVBMMZ x = 0 x
+= 1 ** 2 p x # => Intend: 2 (Keeping current behavior) y = 0 y++ ** 2 p y # => Intend: 1 (Changing current behavior)

"MUFSOBUJWFMZ JUNJHIUCFQPTTJCMFUPDSFBUFBTZOUBYUSFF UIBUXSBQTUIFMFGUIBOETJEFBOEA AJOA AUPDPOUSPM UIFQSFDFEFODFPGFYQSFTTJPOT i = 0
i++ * 2 # => i += (1 * 2) )PXFWFS UIJTXPVMENBLFUIFCFIBWJPSPGUIFTDBOOFS UPPDPNQMJDBUFE

0, MFU`TUIJOLPGBOPUIFSXBZ

5VSOA AJOUPA A 3FWJTFE

*OUIFQSFWJPVTJNQMFNFOUBUJPO XFUSJFEUPNBLFUIF TBNF"45XJUIA ACZUIFTDBOOFS i = 0 i++ * 2
# => i += (1 * 2) p i # => 2 #VUXFGPVOEUIBUJGA AJTGPMMPXFECZBOFYQSFTTJPO XFDBOOPUIBOEMFJU 5VSOA AJOUPA A 3FWJTFE

5PBWPJEUIJT IPXBCPVUDPOTJEFSJOHUIFTFRVFODFPG UIFMFGUIBOETJEFPGUIFFYQSFTTJPOBOE BTBTJOHMF TZOUBYBOEEPJOHUIFTBNFUIJOHUPA ACZUIFQBSTFS i++ 1BSTFBOENBLFBTBNF"45BT
5VSOA AJOUPA A 3FWJTFE

5IFSFBSFUXPOFDFTTBSZUIJOHTUPJNQMFNFOUUIJT 5VSOA AJOUPA A 3FWJTFE

5IFSFBSFUXPOFDFTTBSZUIJOHTUPJNQMFNFOUUIJT "EETZNCPMTBOEHSBNNBSSVMFTUPBMMPX TZOUBYMJLFAJ A 5VSOA AJOUPA A 3FWJTFE

5IFSFBSFUXPOFDFTTBSZUIJOHTUPJNQMFNFOUUIJT "EETZNCPMTBOEHSBNNBSSVMFTUPBMMPX TZOUBYMJLFAJ A %F fi OFBOBDUJPOUIBUEPFTUIFTBNFUIJOH XIFOBTZOUBYMJLFAJ AJTQBSTFE BTXIFOBTZOUBYMJLFAJ
AJTEPOF 5VSOA AJOUPA A 3FWJTFE -FUTHFUUPJU i = 0 i++ # Do the same thing as `i+=1` internally

// ruby/parse.y %token <id> tCOLON2 RUBY_TOKEN(COLON2) "::" %token tCOLON3 "::
at EXPR_BEG" %token <id> tOP_ASGN "operator-assignment" /* +=, -= etc. */ %token <id> tINCOP "increment-operator" %token tASSOC "=>" %token tLPAREN "(" %token tLPAREN_ARG "( arg" %token tRPAREN ")" %token tLBRACK "[" %token tLBRACE “{" %token tSTAR "*" %token tDSTAR "**arg" %token tAMPER "&" // ... %F fi OFTZNCPMU*/$01 'JSTU EF fi OFU*/$01BTUIFTZNCPM GPSUIFUPLFO %F fi OFBOFXTZNCPMGPS

... switch (c = nextc(p)) { // ... case '+': c = nextc(p); // ... if (c == '+') .BLFUIFTDBOOFSSFUVSOU*/$01 5IFONPEJGZQBSTFS@ZZMFY *G JTSFBEUXJDFJOBSPX *GUIFOFYUDIBSBDUFSJTBMTP 3FBEOFYUDIBSBDUFSPGUIF 8IFOUIFDIBSBDUFSSFBEJT

... switch (c = nextc(p)) { // ... case '+': c = nextc(p); // ... if (c == '+') { SET_LEX_STATE(EXPR_BEG); return tINCOP; } // ... .BLFUIFTDBOOFSSFUVSOU*/$01 SFUVSOU*/$01 5IFTDBOOFSNPEJ fi DBUJPOJTOPXDPNQMFUF 3FUVSOU*/$01

// ruby/parse.y arg : lhs '=' lex_ctxt arg_rhs // ...
| var_lhs tOP_ASGN lex_ctxt arg_rhs // ... | ???? %F fi OFBOFXHSBNNBSSVMF /FYU EF fi OFBOFXHSBNNBSSVMFGPSA A 4JODFBHSBNNBSSVMFGPSBTDSJQUTVDIBTAJ AJT EF fi OFEJOQBSTFZ MFUTEF fi OFUIFOFXPOFOFBSIFSF %F fi OFUIFOFXHSBNNBSSVMF "HSBNNBSSVMFGPS 3VCZTDSJQUTMJLFAJ A

// ruby/parse.y arg : // ... | var_lhs lex_ctxt tINCOP
%F fi OFBOFXHSBNNBSSVMF )FSFJTUIFHSBNNBSSVMFUPCFBEEFE 5IFOFXHSBNNBSSVMFDIFDLTUIBUUIFTZNCPMT WBS@MIT MFY@DUYU BOEU*/$01BSFJOBSPX %F fi OFBOFXHSBNNBSSVMF

5IFNJEEMFPOF MFY@DUYU JTOPUTPSFMFWBOUUIJTUJNF TPTLJQJU WBS@MITJTUIFMFGUTJEFPGA A BOEU*/$01JTA A MFY@DUYUJTOPUTPSFMFWBOU TPXFTLJQJU 5IJTNBLFTFYQSFTTJPOTMJLFAJ AWBMJEBTBTZOUBY 5IFTFTZNCPMTNFBOTʜ J # In a Ruby script i++ OPOF %F fi OFBOFXHSBNNBSSVMF

{ // ... %F fi OFBOFXBDUJPOUPEPUIFTBNFUIJOHA AEPFT -FUTOPXEF fi OFUIFBDUJPOUPCFFYFDVUFEVQPO SFEVDJOHUIJTHSBNNBSSVMF

{ SET_LEX_STATE(EXPR_END); 'JSTU DBMM4&5@-&9@45"5&XJUI&913@&/%UPUFMM UIFTDBOOFSUPFOEUIJTFYQSFTTJPO /PUF5IFEF fi OJUJPOTPGBDUJPOTGPS3JQQFSBSFTLJQQFEJOUIJTTMJEF 5FSNJOBUFUIJTFYQSFTTJPO %F fi OFBOFXBDUJPOUPEPUIFTBNFUIJOHA AEPFT

{ SET_LEX_STATE(EXPR_END); ??? /FYU MFUTEPUIFTBNFUIJOHBTA A )PXDBOXFEPUIBU /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF %F fi OFBOFXBDUJPOUPEPUIFTBNFUIJOHA AEPFT

// ruby/parse.y static NODE * new_op_assign(struct parser_params *p, NODE *lhs,
ID op, NODE *rhs, struct lex_context ctxt, const YYLTYPE *loc); OFX@PQ@BTTJHO .3*QSPWJEFTOFX@PQ@BTTJHO UPDSFBUFBO3/PEF UIBUJTBOFYQSFTTJPOXJUIA APSAA -FUTVTFUIJTGVODUJPOUPEPXIBUJTUIFTBNF BTA A

// ruby/parse.y static NODE * new_op_assign(struct parser_params *p, NODE *lhs,
ID op, NODE *rhs, struct lex_context ctxt, const YYLTYPE *loc); OFX@PQ@BTTJHO 4PNFBSHVNFOUTBSFSFRVJSFEUPDBMMUIJTGVODUJPO "O3/PEFUIBUJTUIFWBMVFPOUIFMFGUTJEFPGUIFFYQSFTTJPO "OPQFSBUPS A APSAA "O3/PEFUIBUJTUIFWBMVFPOUIFSJHIUTJEFPGUIFFYQSFTTJPO

{ SET_LEX_STATE(EXPR_END); // ... new_op_assign(p, ???, ???, ???, $2, &@$); } $BMMOFX@PQ@BTTJHO /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF 4PMFUTQSFQBSFUIFBSHVNFOUT UPDBMMOFX@PQ@BTTJHO OFX@PQ@BTTJHO SFRVJSFTBSHVNFOUT

{ SET_LEX_STATE(EXPR_END); // ... new_op_assign(p, $1, '+', ???, $2, &@$); } 1BTTUIFMFGUIBOETJEFPGA ABTUIFTFDPOE BSHVNFOUBOEA ABTUIFUIJSEBSHVNFOU -FGUIBOETJEF /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF $BMMOFX@PQ@BTTJHO

{ SET_LEX_STATE(EXPR_END); // ... new_op_assign(p, $1, '+', ???, $2, &@$); } 5IFGPVSUIBSHVNFOUJTUIFWBMVFPGUIFSJHIUTJEFPG A A*OUIFDBTFPGA A UIFSJHIUTJEFJTBMXBZTBO JOUFHFS TPXFOFFEUPDSFBUFBWBMVFPGUIJT 3FRVJSFTBOJOUFHFSWBMVFAA /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF $BMMOFX@PQ@BTTJHO

{ SET_LEX_STATE(EXPR_END); // ... new_op_assign(p, $1, '+', ???, $2, &@$); } TFU@JOUFHFS@MJUFSBM VTFEJOPOFQSFWJPVT JNQMFNFOUBUJPODBOOPUCFVTFEIFSF BTJUJTBGVODUJPOUPTFUBWBMVFUPBTZNCPM 8FOFFEUPDSFBUFBO3/PEFUIBUJTBOJOUFHFS /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF $BMMOFX@PQ@BTTJHO

{ SET_LEX_STATE(EXPR_END); VALUE v = rb_cstr_to_inum("1", 16, FALSE); NODE *one = NEW_LIT(v, &NULL_LOC); 5PEPUIJT DSFBUFB7"-6&PGJOUFHFS BOEUIFO DSFBUFBO3/PEFUIBUJTMJUFSBMGSPNUIJT7"-6& "7"-6&PGBOJOUFHFS "O3/PFPGBMJUFSBM /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF $BMMOFX@PQ@BTTJHO

{ SET_LEX_STATE(EXPR_END); VALUE v = rb_cstr_to_inum("1", 16, FALSE); NODE *one = NEW_LIT(v, &NULL_LOC); RB_OBJ_WRITTEN(p->ast, Qnil, x); new_op_assign(p, $1, '+', one, $2, &@$); } 5IFOQBTTJUUPUIFGPVSUIBSHVNFOUPG OFX@PQ@BTTJHO 1BTTUIF3/PEFUIBUJTBJOUFHFSMJUFSBM /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF $BMMOFX@PQ@BTTJHO

{ SET_LEX_STATE(EXPR_END); VALUE v = rb_cstr_to_inum("1", 16, FALSE); NODE *one = NEW_LIT(v, &NULL_LOC); RB_OBJ_WRITTEN(p->ast, Qnil, x); $$ = new_op_assign(p, $1, '+', one, $2, &@$); } 'JOBMMZ TFUUIF3/PEF UIFSFUVSOWBMVFPG OFX@PQ@BTTJHO UPUIFTZNCPMBGUFSSFEVDUJPO /PUFUIFEF fi OJUJPOPGBDUJPOTJTTMJHIUMZTJNQMJ fi FEJOUIJTTMJEF "TTJHOUIFSFUVSOWBMVFUPUIFTZNCPMBGUFSSFEVDUJPO $BMMOFX@PQ@BTTJHO

5IFJNQMFNFOUBUJPOPGA AJT OPXDPNQMFUF

3VOUIFEFNP

"MMTXFMMUIBUFOETXFMMʜ

6OGPSUVOBUFMZ UIFBOTXFSJTOP 5IFBEEJUJPOPGUIFA APQFSBUPSJTCSFBLJOH POFFYJTUJOHTZOUBY

*OPSEJOBSZ3VCZ XFDBOVTFBOZOVNCFSPG JO TVDDFTTJPOXJUIPVUDBVTJOHTZOUBYFSSPST # Normal Ruby i = 0
i + 1 # => 1 i ++ 1 # => 1 i +++ 1 # => 1 i ++++ 1 # => 1 i +++++ 1 # => 1 5IJTJTCFDBVTFJGUIFSFBSFUXPPSNPSF T UIFTFDPOEBOETVCTFRVFOU TBSFDPOTJEFSFE VOBSZ PQFSBUPST "MM`T/05XFMMUIBUFOETXFMM "MMTZOUBY0,

#VUJO3VCZXJUI PQFSBUPS XFHFUBTZOUBYFSSPSXJUIVOFYQFDUFEJOUFHFSMJUFSBM JGXFUSZUPQVUBOJOUFHFSBGUFSA A # Ruby with "++"
operator # ruby/test.rb i = 0 i + 1 # => 1 i ++ 1 # => SyntaxError i = 0 i + (+1) # => 1 i ++ +1 # => 3 "MM`T/05XFMMUIBUFOETXFMM SVCZSVCZUFTUSC SVCZUFTUSCSVCZUFTUSC TZOUBYFSSPS VOFYQFDUFEJOUFHFSMJUFSBM FYQFDUJOHFOEPGJOQVU 4ZOUBY&SSPS J J ? 5IFZBSFTZOUBY0, ɾ5PVTFBVOBSZPQFSBUPSXJUIQBSFOUIFTFT ɾ5PVTFA ABOEBVOBSZPQFSBUPSBUUIFTBNFUJNF

*TUIJTBWBMJETQFDJ fi DBUJPO )PXTIPVMEUIF PQFSBUPSBOEVOBSZPQFSBUPST DPPQFSBUFXJUIFBDIPUIFS 5IFTFBSFRVFTUJPOTUIBUTIPVMECFDPOTJEFSFEJO3VCZ UIBUBEEFEUIFOFXTZOUBYXJUIUIF
PQFSBUPS 5IJTJTBOJTTVFPGMBOHVBHFEFTJHO 'PSUIFNPNFOU UIJTJTUIFTQFDJ fi DBUJPOPGUIF JNQMFNFOUBUJPOTPGBS 5IFMBOHVBHFEFTJHOBGUFSBEEJOHBOFXTZOUBY

8FDBOOPMPOHFSDBMMUIJT3VCZ CFDBVTF*IBWFDIBOHFEUIFFYJTUJOHTZOUBY 5IJTOFXMBOHVBHFOFFETBOFXOBNF TPNFUIJOHBQQSPQSJBUFGPSJU

3VCZ 3VCZ

3VCZ 3VCZ IUUQTHJUIVCDPNTIJPJNNSVCZQMVTQMVT

&QJMPHVF

!TQJLFPMBGUPMENFʜ SFGIUUQTUXJUUFSDPNTQJLFPMBG

5IFSFBSFUXPUZQFTPGQFPQMF 0OFJTXIPOFFETBOFXHSBNNBSSVMF UPBEEBOFXTZOUBYJOUP.3* BOEPUIFSTXIPEPO`U

5IFSFBSFUXPUZQFTPGQFPQMF 0OFJTXIPOFFETBOFXHSBNNBSSVMF UPBEEBOFXTZOUBYJOUP.3* BOEPUIFSTXIPEPO`U "EEJOHOFXTZOUBYPOMZCZMFYJDBMBOBMZTJT

8IBUUIJTNFBOTJTUIBUBMUIPVHI*FWFOUVBMMZBEEFE BOFXTZOUBYSVMFGPS PQFSBUPSUIJTUJNF UIFSFBSFQSPCBCMZPUIFSXBZTUPEPJUUIBU*IBWFOPU EJTDPWFSFEJOQSBDUJDF

"OEOPUKVTU PQFSBUPS UIFSFXJMMCFBTNBOZXBZTUPBEEOFXTZOUBYUP .3*BTJNQMFNFOUPSTDBODPNFVQXJUI

"OEBT*IBWFTIPXO .3*IBTNBOZVTFGVMUPPMLJUTGPS SFBMJ[JOHUIFTFJEFBT 7BSJPVTUPPMLJUTUPTVQQPSUZPVSJEFB 'PSFYBNQMF )PXUPNPEJGZUIFTDBOOFS QBSTFS@ZZMFY )PXUPEF fi
OFOFXTZOUBYSVMFTBOEBDUJPOTXJUITFNBOUJDWBMVFT 8IBUJTUIFPCKFDUPSJFOUFETFNBOUJDT "NBDSPUPDIBOHFUIFTUBUFPGUIFTDBOOFS 4&5@-&9@45"5& 4PNFVTFGVMGVODUJPOTUPDSFBUF3/PEFT FHOFX@RDBMM OFX@PQ@BTHO 4PNFVTFGVMNBDSPTUPDSFBUF3/PEFT FH/&8@-*5 /&8@7$"-- /&8@-*45 5IFMPDBUJPOBMJOGPSNBUJPOPGUIFTDBOOFSBOETPNFVTFGVMGVODUJPOT UPQFFLBUUIFDIBSBDUFSPOBTPVSDFDPEF FHQFFLD QFFLD@O

#ZNBLJOHGVMMVTFPGUIFN XIPBEET BOFXTZOUBYUP.3*OFYUJOPUIFSXBZT ʜJUNBZCFZPV

5IBOLZPVGPSZPVSBUUFOUJPO 4QFDJBMUIBOLTUP !TQJLFPMBG !NJOFSPBPLJ !PLVSBNBTBGVNJ 3FGFSFODFUP 3VCZ)BDLJOH(VJEF 1BSU4ZOUBYBOBMZTJT IUUQTSVCZIBDLJOHHVJEFHJUIVCJP
3VCZ6OEFSB.JDSPTDPQF"O*MMVTUSBUFE(VJEFUP3VCZ*OUFSOBMT $IBQUFS5PLFOJ[BUJPOBOE1BSTJOH IUUQTQBUTIBVHIOFTTZOFUSVCZVOEFSBNJDSPTDPQF

'PSXIFOUIFEFNPEPFTOUXPSL

3VOXJUIDPNQJMFE3VCZ

Implementing "++" operator, stepping into parse.y

Implementing "++" operator, stepping into parse.y

More Decks by Misaki Shioi(塩井美咲/しおい)

Other Decks in Programming

Featured

Transcript