RosettaCodeData/Task/Four-is-magic/ALGOL-68/four-is-magic.alg
2025-02-27 18:35:13 -05:00

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BEGIN # construct number names from a number #
MODE NUMBER = LONG INT; # adjust to suit, must be at least 64 bits #
OP TOINT = ( NUMBER n )INT: SHORTEN n; # adjust to suit #
[]STRING units
= ( "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" );
[]STRING teens
= ( "ten", "eleven", "twelve", "thirteen", "fourteen"
, "fifteen", "sixteen", "seventeen", "eighteen", "nineteen"
);
[]STRING tens
= ( "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety" );
[]STRING power suffix
= ( "thousand", "million", "billion", "trillion", "quadrillion", "quintillion" );
# returns n converted to a number name, n must be in range 1-99 #
PROC two digits = ( INT n )STRING:
IF n < 10
THEN units[ n ]
ELIF n < 20
THEN teens[ n - 9 ]
ELIF INT last1 = n MOD 10;
last1 = 0
THEN tens[ ( n OVER 10 ) - 1 ]
ELSE tens[ ( n OVER 10 ) - 1 ] + " " + units[ last1 ]
FI # two digits # ;
# returns n converted to a number name, n must be in range 1-999 #
PROC three digits = ( INT n )STRING:
IF n < 100
THEN two digits( n )
ELIF STRING hundreds = units[ n OVER 100 ] + " hundred";
INT last2 = n MOD 100;
last2 = 0
THEN hundreds
ELSE hundreds + " " + two digits( last2 )
FI # three digits # ;
# returns the "name" of n #
OP NAME = ( NUMBER n )STRING:
IF n < 0 THEN "negative " + NAME - n
ELIF n = 0 THEN "zero"
ELSE # have a positive number to name #
NUMBER v := n;
STRING result := "";
INT power pos := 0;
WHILE v /= 0 DO
IF INT v999 = TOINT ( v MOD 1000 );
v999 /= 0
THEN STRING component := three digits( v999 );
IF power pos > 0 THEN
component +:= " " + power suffix[ power pos ]
FI;
IF result /= "" THEN component +:= " " FI;
component +=: result
FI;
power pos +:= 1;
v OVERAB 1000
OD;
result
FI # NAME # ;
# returns the "x is y, y is z, ... four is magic" sequence derived from n #
OP MAGIC = ( NUMBER n )STRING:
BEGIN
NUMBER v := n;
STRING result := "";
WHILE v /= 4 DO
IF result /= "" THEN result +:= ", " FI;
STRING v name = NAME v;
v := ( UPB v name - LWB v name ) + 1;
result +:= v name + " is " + NAME v
OD;
IF result /= "" THEN result +:= ", " FI;
result + "four is magic"
END # MAGIC # ;
# test cases #
[]NUMBER t = ( 0, 1, 2, 3, 4, 5, 100, 101, 272, 1701, 1968, 4077, 90 210
, - 100 001, 987 654, - NUMBER( 8 007 006 005 004 003 )
);
FOR n FROM LWB t TO UPB t DO
print( ( whole( t[ n ], -18 ), ": ", MAGIC t[ n ], newline ) )
OD
END