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/*
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Crown Copyright (c) 1997
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This TenDRA(r) Computer Program is subject to Copyright
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owned by the United Kingdom Secretary of State for Defence
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acting through the Defence Evaluation and Research Agency
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(DERA). It is made available to Recipients with a
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royalty-free licence for its use, reproduction, transfer
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to other parties and amendment for any purpose not excluding
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product development provided that any such use et cetera
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shall be deemed to be acceptance of the following conditions:-
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(1) Its Recipients shall ensure that this Notice is
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reproduced upon any copies or amended versions of it;
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(2) Any amended version of it shall be clearly marked to
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show both the nature of and the organisation responsible
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for the relevant amendment or amendments;
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(3) Its onward transfer from a recipient to another
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party shall be deemed to be that party's acceptance of
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these conditions;
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(4) DERA gives no warranty or assurance as to its
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quality or suitability for any purpose and DERA accepts
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no liability whatsoever in relation to any use to which
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it may be put.
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*/
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/*
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** primes2.pl:
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**
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** Same as primes.pl but with suitable general procedures.
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*/
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/* Define a recursive data structure */
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Struct Chain (a:Int, b:pointer(Chain_Align));
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Al_tagdef Chain_Align = alignment (Chain);
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Iddec printf : proc;
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Iddec falls_through_sieve : proc;
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Iddec apply_sieve : proc;
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Var count_down : Int;
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Var next_integer : Int;
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Var global_chain : pointer(Chain_Align);
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String first = "The first %d primes:\n\n";
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String s = "%d\n";
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Proc falls_through_sieve = General Int (; z:pointer(Chain_Align) ... ) Untidy
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{
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? { *? ((* z) == make_null_ptr(Chain_Align));
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untidy_return (0(Int))
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make_top
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};
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Let a_z = a [(*(Chain) (* z))]
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{
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? { ? ((a_z * a_z) > (* next_integer));
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return (0(Int))
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make_top
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};
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? { ? (((* next_integer) % a_z) == 0(Int));
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untidy_return (1(Int))
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z = b [(*(Chain) (* z))];
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falls_through_sieve Tail_call [Same ... ]
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}
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}
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};
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Proc apply_sieve = General top (; z:pointer(alignment(pointer(Chain_Align))) ... ) Untidy
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Var link : Chain
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{
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? { ? ((* count_down) < 1(Int));
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return (make_top)
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make_top
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};
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? { ? (falls_through_sieve [Int] [; (* global_chain) ... ] != 0(Int));
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next_integer = ((* next_integer) + 1(Int));
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apply_sieve Tail_call [Same ... ];
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(link *+. .a) = (* next_integer);
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(link *+. .b) = make_null_ptr (Chain_Align);
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(* z) = link;
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printf [top] (s, (* next_integer));
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next_integer = ((* next_integer) + 1(Int));
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count_down = ((* count_down) - 1(Int));
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z = (link *+. .b);
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apply_sieve [top] [; Same ... ]; /* Cannot be a tail call */
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};
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untidy_return (make_top)
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};
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Proc sieve = top (n:Int)
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{
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printf [top] (first, (* n));
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count_down = (* n);
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next_integer = 2(Int);
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global_chain = make_null_ptr (Chain_Align);
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apply_sieve Tail_call [global_chain ... ];
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};
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Proc main = top ()
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{
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sieve [top] (25(Int));
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return (make_top)
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};
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Keep(main, sieve, apply_sieve, falls_through_sieve,
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first, s, global_chain, next_integer, count_down,
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Chain, Chain_Align)
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