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<HTML><HEAD><TITLE>Answer to Exercise 72</TITLE></HEAD>
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<BODY BGCOLOR="#FFFFFF">
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<TABLE><TR><TD Valign="top"><IMG SRC="../icons/exercise.gif" ALT="??"><TD bgcolor="#FAA89B"><B>ANSWER TO EXERCISE 72</B><TR><TD><TD>
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be returned as a number in the usual Inform time format:
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as hours times 60 plus minutes (on the 24-hour clock, so
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that the 'hour' part is between 0 and 23).
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Constant TWELVE_HOURS = 720;
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[ NumericTime hr mn word x;
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if (hr>=24) return -1;
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if (mn>=60) return -1;
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x=hr*60+mn; if (hr>=13) return x;
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x=x%TWELVE_HOURS; if (word=='pm') x=x+TWELVE_HOURS;
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if (word~='am' or 'pm' && hr==12) x=x+TWELVE_HOURS;
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[ MyTryNumber wordnum i j;
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i=wn; wn=wordnum; j=NextWordStopped(); wn=i;
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{ 'twenty-five': return 25;
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default: return TryNumber(wordnum);
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[ TimeOfDay i j k flag loop ch hr mn;
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{ 'midnight': parsed_number=0; return 1;
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'midday', 'noon': parsed_number=TWELVE_HOURS; return 1;
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! Next try the format 12:02
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j=WordAddress(wn-1); k=WordLength(wn-1);
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for (loop=0:loop<k:loop++)
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if (ch==':' && flag==0 && loop~=0 && loop~=k-1) flag=1;
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else { if (ch<'0') flag=-1; if (ch>'9') flag=-1; }
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if (k<3) flag=0; if (k>5) flag=0;
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{ for (loop=0:j->loop~=':':loop++, hr=hr*10)
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hr=hr+j->loop-'0';
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for (loop++:loop<k:loop++, mn=mn*10)
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mn=mn+j->loop-'0';
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parsed_number=NumericTime(hr, mn, j);
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if (parsed_number<0) return -1;
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if (j~='pm' or 'am') wn--;
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! Next the format "half past 12"
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j=-1; if (i=='half') j=30; if (i=='quarter') j=15;
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if (j<0) j=MyTryNumber(wn-1); if (j<0) return -1;
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if (j>=60) return -1;
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{ hr=j; if (hr>12) return -1; jump TimeFound; }
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if (k=='o^clock' or 'am' or 'pm')
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{ hr=j; if (hr>12) return -1; jump TimeFound; }
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if (k=='to' or 'past')
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{ mn=j; hr=MyTryNumber(wn);
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{ switch(NextWordStopped())
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{ 'noon', 'midday': hr=12;
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if (hr>=13) return -1;
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if (k=='to') { mn=60-mn; hr=hr-1; if (hr==-1) hr=23; }
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wn++; k=NextWordStopped();
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hr=j; mn=MyTryNumber(--wn);
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if (mn<0) return -1; if (mn>=60) return -1;
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wn++; k=NextWordStopped();
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parsed_number = NumericTime(hr, mn, k);
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if (parsed_number<0) return -1;
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if (k~='pm' or 'am' or 'o^clock') wn--;
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<HR>Back to <A HREF="../section27.html#ex72">the exercise in section 27</A><HR>
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<SMALL><I>Mechanically translated to HTML from third edition as revised 16 May 1997. Copyright © Graham Nelson 1993, 1994, 1995, 1996, 1997: all rights reserved.</I></SMALL></BODY></HTML>
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