Algol 68 - ACM Digital Library

28 van Wijngaarden, et aLALGOL 68 Revised Report29not necessarily that found in a dictionary but can be construed from therules which follow.}a) A "paranotion" P is a hypernotion {not between apostrophes} whichis used, in the text of this Report, to "designate" any construct whoseoriginal O satisfies the following:• P, regarded as a hypernotion {i.e., as if it had been enclosed inapostrophes}, designates {l.l.4.1.a} an "abstraction" {b} of O.{For example, the paranotion "fixed-point-numeral" could designate theconstruct represented by 02, since, had it been in apostrophes, it wouldhave designated an abstraction of the notion 'fixed point numeral', whichis the original of that construct. However, that same representation couldalso be described as a digit-cypher.sequence, and as such it would be adirect descendent of that fixed-point-numeral.}{As an aid to the reader in distinguishing them from otherhypernotions, paranotions are not enclosed between apostrophes and areprovided with hyphens where, otherwise, they would have been providedwith blanks.}The meaning of a paranotion to which the small syntactic mark "s" hasbeen appended is the same as if the letter "s" {which is in the same typefont as the marks in this sentence} had been appended instead. {Thus thefixed-point-numeral 02 may be said to contain two digit-cyphers, ratherthan two digit-cyphers.} Moreover, the "s" may be inserted elsewhere thanat the end if no ambiguity arises {e.g., "sources-for-MOI)lNE" means thesame as "source-for.MOI)lNEs"}.An initial small syntactic mark of a paranotion is often replaced by thecorresponding large syntactic mark {in order to improve readability, as atthe start of a sentence} without change of meaning {: e.g., "Identifier"means the same as "identifier"}.b) A protonotion P2 is an "abstraction" of a protonotion P1 if(i) P2 is an abstraction of a notion whose production rule begins with anasterisk and of which Pl is an alternative{e.g., "trimscript' (5.3.2.1.h) is an abstraction of any of thenotions designated by 'NEST trimmer', 'NEST subscript' and'NEST revised lower bound option'}, or(if) P1 envelops a protonotion ?3 which is designated by one of the"elidible hypernotions" listed in section c below, and ?2 is anabstraction of the protonotion consisting of ?1 without that envelopedP3{e.g., 'choice using boolean start' is an abstraction of the notions'choice using boolean brief start" and 'choice using boolean boldstart' (by elision of a 'STYLE' from 9.1.1.a)}, or(iii) P2 is equivalent to {2.1.1.2.a} Pl{e.g., 'bold begin symbol"symbol'}.is an abstraction of 'bold begin{For an example invoking all three rules, it may be observed that'union of real integral mode defining indicator' is an abstraction of some'union of integral real mode NEST defining identifier with letter a'(4.8.1.a). Note, however, that "choice using union of integral real modebrief start' is not an abstraction of the notion 'choice using union ofintegral real boolean mode brief start', because the 'boolean' that hasapparently been elided is not an enveloped 'MOLD" of that notion.}c) The "elidible hypernotions" mentioned in section b above are thefollowing:"STYLE" • "TALLY" • "LEAP" • "DEFIED" • "VICTAI." •"SORT" • "MOLD" • "NEST" • "REFETY routine" • "label" •"with TAX" • "with DECSETY LABSETY" • "of DECSET'~ I,ABSETY" •"defining LAYER".{Which one of several possible notions or symbols is the original of aconstruct designated by a given paranotion will be apparent from thecontext in which that paranotion appears. For example, when speaking ofthe formal-declarer of an identity-declaration, if the identity-declaration isone whose terminal production (1.1.3.2.f) happens to be rot realx = Ioc real,then the original of that formal-declarer is some notion designated by'formal reference to real NEST declarer'.}{Since a paranotion designates a construct, all technical terms whichare defined for constructs can be used with paranotions without formality.}d) If two paranotions P and Q designate, respectively, two constructsS and T, and if S is a descendent of T, then P is termed a "constituent" ofQ unless there exists some {intermediate construct} U such that(i) S is a descendent of U,(if) U is a descendent of T, and(iii) either P or Q could {equally well} designate U.{Hence a (S1) is a constituent operand of the formula ax(b+2 r (i+j))(T), but b ($2) is not, since it is a descendent of an intermediate formulab+2 I (i+j) (U), which is itself descended from T. Likewise, (b+2 T (i+j))is a constituent closed-clause of the formula T, but the closed-clause (i+j)is not, because it is descended from an intermediate closed-clause.However, (i + j) is a constituent integral-closed.clause of T, because theintermediate closed-clause is, in fact, a real-closed-clause.