Algol 68 - ACM Digital Library

122 van Wijngaarden, et al.style ii comment symbol{92b}bold pragmat symbol192b}style i pragmat symbol{92b}9.4.2. Other TAX symbols9.4.2.1. MetasyntaxpragmatprA) TA(; {D,F,K,48a,b,c,d} ::I,EI"TER{B} ;TAG I,ETTER{B} ; TAG DIGIT{C}.B) LETI"ER{A} : :letter ABC{94a} ; letter aleph{-} ; style "l'Al.l.~ letter ABC{-}.C) DIGIT{A} ..: digit zero{94b} ; digit one{94b} ; digit two{94b} ;digit three{94b} ; digit four{94b} ; digit five{94b} ; digit six{94b} ;digit seven{94b} ; digit eight{94b} ; digit nine{94b}.D) TAB{48a,b} :: bold TAG{A,-} ; SIZETY STANDARD{E}.E) STANDARD{D} .... integral{94e} ; reai{94e} ; boolean{94e} ;charaeter{94e} ; format{94e} ; void{94e} ; eomplex{94e} ; bits{94e} ;bytes{94e} ; string{94e} ; sema{94e} ; file{94e} ; ehannel{94e}.F) TAD{48a,b} ..: bold TAG{A,-} ; DYAD{G} BECOMESETY{J} ;DYAD{G} cum NOMAD{I} BEEOMESETY{J}.G) DYAD{F} :: MONAD{H} ; NOMAD{I}.H) MONAD{G,K} :: or{94c} ; and{94e} ; ampersand{94c} ;differs from{94c} ; is at most{94c} ; is at least{94c} ; over{94c} ;percent{94c} ; window{94c} ; floor{94c} ; ceiling{94c} ;plus i times{94c} ; not{94c} ; tilde{94c} ; down{94c} ; up{94c} ;plus{94e} ; minus{94c} ; style TALLY monad{-}.I) NOMAD{F,G,K} :: is less than{94c} ; is greater than{94c} ;divided by{94e} ; equals{94c} ; times{94c} ; asterisk{94e}.J) BECOMESETY{F,K} :: cum beeomes{94c} ; cum assigns to{94c} ;EMPTY.K) TAM{48a,b} :: bold TAG{A,-} ; MONAD{H} BECOMESETY{J} ;MONAD{H} cum{9422e} NOMAD{I} BECOMESETY{J}.L) ABC{B}:: a;b;e ;d;e;f;g;h ;i;j ;k;! ;m ;n;o;p;q;r;s;t;u;v;w;x;y;z.M) * DOP :: DYAD{G} ; DYAD{G} cum NOMAD{I}.{The metanotion "ABC" is provided, in addition to the metanotion"ALPHA", in order to facilitate the definition of variants of ALGOL 68(l.l.5.b) .}9.4.2.2. Representationa) The representation Of each TAG-symbol not given above {9.4.1} iscomposed of marks corresponding, in order, to the "LETTER's or 'DIGIT'scontained in that 'TAG'. These marks may be separated by typographicalALGOL 68 Revised Report 123display features {9.4.d}. The mark corresponding to each 'LETTER"('DIGIT') is the representation of that LETTER-symbol (DIGIT-symbol).{For example, the representation of a letter-x-digit-one-symbol is xl, whichmay be written x l. TAG-symbols are used for identifiers and fieldselectors.}b) The representation, if any, of each bold-TAG-symbol is composed ofmarks corresponding, in order, to the 'LETTER's or 'DIGIT's contained inthat 'TAG" {but with no typqgraphical display features in between}. Themark corresponding to each 'LETTER' ('DIGIT') is similar to the markrepresenting the corresponding LETTER-symbol (DIGIT-symbol), being, inthis Report, the corresponding bold faced letter (digit). {Other methods ofindicating the similarity which are recognizable without furtherelucidation are also acceptable, e.g., person, person, PERSON, 'person and'person' could all be representations of the bold-letter-p-letter.e-letter-rietter-s-letter.o.letter.n.symbol.}However, the representation of a bold-TAG-symbol may not be thesame as any representation of any other symbol {; thus there may be afinite number of bold-TAG.symbols which have no representation; e.g.,there is no representation for the bold-letter-r-letter.e-letter-a-letter.l.symbol because real is a representation of the real.symbol; note that thenumber of bold-TAG-symbols available is still arbitrarily large}. If,according to the convention used, a given sequence of marks could beeither the representation of one bold-TAG-symbol or the concatenation ofthe representations of two or more other symbols, then it is always to beconstrued as that one symbol {; the inclusion of a blank can always forcethe other interpretation; e.g., refreal is one symbol, whereas refreel mustalways be two}. {Bold-TAG-symbols are used for mode.indications and foroperators.}e) The representation of each SIZE-SIZET~(-STANDARD.symbol iscomposed of the representation of the corresponding SIZE-symbol, possiblyfollowed by typographical display features, followed by the represention ofthe corresponding SIZETY-STANDARD-symbol. {For example, therepresentation of a long-real-symbol is Iong real, or perhaps 'long"real'(but not, according to section b above, Iongreal or 'longreal', for thosewould be representations of the bold-letter.l.letter.o.letter.n.letter.g.letter.r.letter-e-letter-a-letter-l-symbol). SIZETY-STANDARD.symbols are used formode-indications.}d) The representation of each DOP-cum-becomes-symbol (DOP-cumassigns-to-symbol)is composed of the mark or marks representing thecorresponding DOP-symbol followed {without intervening typographicaldisplay features} by the marks representing the becomes-symbol (theassigns-to-symbol). {For example, the representation of a plus-cumbecomes-symbolis +:=. DOP-cum-beeomes-symbols are used foroperators.}