Algol 68 - ACM Digital Library

124 van Wijngaarden, etal.ALGOL 68 Revised Report125e) The representation of each I)YAD-cum-NOMAI)-symbol is composedof the mark representing the corresponding I)~AI)-symbol followed{without intervening typographical display features} by the markrepresenting the corresponding NOMAD-symbol. {For example, therepresentation of an over-cum-times-symbol is +x. I)YAI)-cum-NOMAI)-symbols are used for operators, but note that NOMAI)I-cum-NOMAI)2-symbols may be only dyadic-operators.}10. Standard environmentPART VEnvironment and Examples{The "standard environment" encompasses the constituent EXTERNALpreludes,system-tasks and particular-postludes of a program-text.}10.1. Program texts{The programmer is concerned with particular-programs (lO.l.l.g).These are always included in a program-text (lO.l.l.a) which also containsthe standard-prelude, a library-prelude, which depends upon theimplementation, a system-prelude and system-tasks, which correspond tothe operating environment, possibly some other particular-programs, oneor more particular-preludes (one for each particular-program) and one ormore particular-postludes.}10.1.1. SyntaxA) EXTERNAL :: standard ; library ; system ; particular.B) STOP :: label letter s letter t letter o letter p.a) program text : STYLE begin{94f} token, new LAYERI preludes{b}, [parallel{94f} token, new LAYERI tasks{d} PACK,STYLE end{94f} token.b) NESTI preludes{a} : NESTI standard prelude with DECSI{c},NESTI library prelude with DECSETY2{c},NESTI system prelude with DECSETY3{c}, where (NESTI) is(new EMPTY new DECSI DECSETY2 DECSETY3).c) NESTI EXTERNAL prelude with DECSETYI{b,f} :strong void NESTI series with DECSETYI{32b}, go on{94f} token ;where (DECSETYI) is (EMPTY), EMPTY.d) NESTI tasks{a} : NESTI system task{e} list, and also{94f} token,NESTI user task{f} PACK list.e) NESTI system task{d} : strong void NESTI unit{32d}.f) NESTI user task{d} : NEST2 particular prelude with I)ECS{c),NEST2 particular program{g} PACK, go on{94f} token,NEST2 particular postlude{i},where (NEST2) is (NESTI new DECS STOP).g) NEST2 particular program{f} :NEST2 new LABSETY3 joined label definition of I.ABSETY3{h},strong void NEST2 new LABSETY3ENCLOSED clause{31a,33a,c,34a,35a}.h) NEST joined label definition of LABSETY{g,h} :where (LABSETY) is (EMPTY), EMPTY ;where (LABSETY) is (LABI LABSETYI),NEST label definition of LABI{32c},NEST joined label definition of LABSETY! {h}.i) NEST2 particular postlude{f} :strong void NEST2 series with STOP{32b}.{Examples:a) ( v standard-prelude v; v library-prelude v; v system-prelude ¢;par begin v system-task-1 v, ¢ system-task-2 v,(¢ particular-prelude v;(start: commence: begin skip end);c particular-postlude c ),( c another user-task c)end)b) c standard-prelude (10.2, 10.3)c; c library-prelude c;c system-prelude (10.4.1) c;d) c system-task-1 (10.4.2.a) c, c system-task-2 c,( c particular-prelude c;(start: commence: begin skip end);c particular-postlude c),(c another user-task c)f) cparticular-prelude (10.5.1)c;(start: commence: begin skip end);cparticular-postlude {10.5.2) cg) start: commence: begin skip endh) start: commence:i) stop: lock (stand in); lock (stand out); lock (stand back) }10.1.2. The environment conditiona) A program in the strict language must be akin {1.1.3.2.k} to someprogram-text whose constituent EXTERNAL-preludes and particularpostludesare as specified in the remainder of this section.{It is convenient to speak of the standard-prelude, the library'.prelude,the particular-programs, etc. of a program when discussing those parts ofthat program which correspond to the constituent standard-prelude, etc. ofthe corresponding program-text.}