Algol 68 - ACM Digital Library

114van Wijngaarden, et al.ALGOL 68 Revised Report 115d)e)f)g)h)CHOICE STYLE out{341} :where (CHOICE) is (choice using boolean),STYLE else{94f,-} token ;where (CHOICE) is (CASE), STYLE out{94f,-} token.CHOICE STYLE finish{34a} :where (CHOICE) is (choice using boolean),STYLE fi{94f,-} token ;where (CHOICE) is (CASE), STYLE esac{94f,-} token.NOTION token : pragment{92a} sequence option,NOTION symbol{94a,b,c,d,e, f,g,h}.* token : NOTION token{f}.* symbol : NOTION symbol{94a,b,c,d,e,f,g,h}.9.2. Comments and pragmats{A source of innocent merriment.Mikado,W.S.Gilbert.}{A pragment is a comment or a pragmat. No semantics of pragmentsis given and therefore the meaning (2.1.4.1.a) of any program is quiteunaffected by their presence. It is indeed the intention that commentsshould be entirely ignored by the implementation, their sole purpose beingthe enlightenment of the human interpreter of the program.Pragmats may, on the other hand, convey to the implementation somepiece of information affecting some aspect of the meaning of the programwhich is not defined by this Report, for example:• the action to be taken upon overflow (2.1.4.3.h) or if the scoperule is violated (as in 5.2.1.2.b), e.g., proverflow check onpr,pr overflow check off pr. pr scope check on pr or pr scope check off pr:• the action to be taken upon completion of the compilationprocess, e.g., pr compile only pr, pr dump pr or pr run pr:• that the language to be implemented is some sublanguage orsuperlanguage of ALGOL 68, e.g., prnonrecpr (for a routine-textwhich may be presumed to be non-recursive):• that the compilation may check for the truth, or attempt to provethe correctness, of some assertion, e.g.:int a, b; read((a, b)) pr assert a >_0 ^ b > O pr;intq:=O,r:=a;while r >_ b pr assert a = b x q + r a 0