Special neighbor primes: Difference between revisions
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=={{header|PL/M}}== |
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{{works with|8080 PL/M Compiler}} ... under CP/M (or an emulator) |
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<syntaxhighlight lang="plm"> |
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100H: /* FIND SOME PAIRS OF PRIMES P, Q BETWEEN 1 AND 99 SUCH THAT P + Q -1 */ |
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/* IS ALSO A PRIME */ |
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/* CP/M BDOS SYSTEM CALL AND I/O ROUTINES */ |
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BDOS: PROCEDURE( FN, ARG ); DECLARE FN BYTE, ARG ADDRESS; GOTO 5; END; |
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PR$CHAR: PROCEDURE( C ); DECLARE C BYTE; CALL BDOS( 2, C ); END; |
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PR$STRING: PROCEDURE( S ); DECLARE S ADDRESS; CALL BDOS( 9, S ); END; |
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PR$NL: PROCEDURE; CALL PR$STRING( .( 0DH, 0AH, '$' ) ); END; |
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PR$NUMBER: PROCEDURE( N ); |
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DECLARE N ADDRESS; |
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DECLARE V ADDRESS, N$STR( 6 ) BYTE, W BYTE; |
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V = N; |
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W = LAST( N$STR ); |
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N$STR( W ) = '$'; |
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N$STR( W := W - 1 ) = '0' + ( V MOD 10 ); |
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DO WHILE( ( V := V / 10 ) > 0 ); |
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N$STR( W := W - 1 ) = '0' + ( V MOD 10 ); |
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END; |
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CALL PR$STRING( .N$STR( W ) ); |
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END PR$NUMBER; |
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/* TASK */ |
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DECLARE FALSE LITERALLY '0'; |
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DECLARE TRUE LITERALLY '0FFH'; |
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DECLARE MAX$LOW$PRIME LITERALLY '99'; |
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DECLARE PRIME ( 200 )BYTE; |
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/* THE SIZE OF PRIME SHOULD BE AT LEAST MAX$LOW$PRIME DOUBLED */ |
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/* SIEVE THE PRIMES TO MAX$PRIME */ |
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DECLARE ( P, Q, COUNT ) ADDRESS; |
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PRIME( 1 ) = FALSE; PRIME( 2 ) = TRUE; |
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DO P = 3 TO LAST( PRIME ) BY 2; PRIME( P ) = TRUE; END; |
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DO P = 4 TO LAST( PRIME ) BY 2; PRIME( P ) = FALSE; END; |
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DO P = 3 TO MAX$LOW$PRIME + 1; |
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IF PRIME( P ) THEN DO; |
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DO Q = P * P TO LAST( PRIME ) BY P + P; PRIME( Q ) = FALSE; END; |
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END; |
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END; |
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/* FIND AND SHOW THE SPECIAL NEIGHBOUR PRIMES */ |
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COUNT = 0; |
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P = 2; |
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Q = 3; |
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DO WHILE Q < MAX$LOW$PRIME; |
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IF PRIME( Q ) THEN DO; |
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DECLARE SNP ADDRESS; |
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SNP = P + Q - 1; |
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IF PRIME( SNP ) THEN DO; |
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/* P AND Q ARE SPECIAL NEIGHBOUR PRIMES */ |
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CALL PR$STRING( .'( $' ); |
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IF P < 10 THEN CALL PR$CHAR( ' ' ); |
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CALL PR$NUMBER( P ); |
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CALL PR$STRING( .' + $' ); |
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IF Q < 10 THEN CALL PR$CHAR( ' ' ); |
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CALL PR$NUMBER( Q ); |
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CALL PR$STRING( .' ) - 1 = $' ); |
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IF SNP < 100 THEN CALL PR$CHAR( ' ' ); |
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IF SNP < 10 THEN CALL PR$CHAR( ' ' ); |
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CALL PR$NUMBER( SNP ); |
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CALL PR$NL; |
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END; |
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P = Q; |
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END; |
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Q = Q + 1; |
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END; |
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EOF |
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</syntaxhighlight> |
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{{out}} |
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<pre> |
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( 3 + 5 ) - 1 = 7 |
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( 5 + 7 ) - 1 = 11 |
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( 7 + 11 ) - 1 = 17 |
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( 11 + 13 ) - 1 = 23 |
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( 13 + 17 ) - 1 = 29 |
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( 19 + 23 ) - 1 = 41 |
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( 29 + 31 ) - 1 = 59 |
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( 31 + 37 ) - 1 = 67 |
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( 41 + 43 ) - 1 = 83 |
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( 43 + 47 ) - 1 = 89 |
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( 61 + 67 ) - 1 = 127 |
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( 67 + 71 ) - 1 = 137 |
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( 73 + 79 ) - 1 = 151 |
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</pre> |
</pre> |
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