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From: guy@rlgvax.UUCP (Guy Harris)
Newsgroups: net.lang
Subject: Re: Strong Typing and Ignorance
Message-ID: <1512@rlgvax.UUCP>
Date: Sat, 31-Dec-83 16:05:09 EST
Article-I.D.: rlgvax.1512
Posted: Sat Dec 31 16:05:09 1983
Date-Received: Sun, 1-Jan-84 02:28:19 EST
References: <2892@utcsrgv.UUCP>, <137@csd1.UUCP> <718@cbosgd.UUCP>, <217@kobold.UUCP> <6421@unc.UUCP>
Organization: CCI Office Systems Group, Reston, VA
Lines: 23

<FIX ME!>

	The "?:" operator, which is a distributed conditional, can have
	differently typed alternative values.  For instance, in the expression
	"i>0 ? 1 : 4.2", the type of the value of the expression cannot be
	determined until the value of i is known -- it might be int, or double.  I
	don't know of any other exceptions to strong typing in C.

According to the C Reference Manual:

	7.13 Conditional operator

	...If possible, the usual arithmetic conversions are performed
	to bring the second and third expressions to a common type;
	otherwise, if both are pointers of the same type, the result
	has the common type; otherwise, one must be a pointer and the
	other the constant 0, and the result has the type of the pointer.

So the type of "i>0 ? 1 : 4.2" is double; the "1" is coerced to double
so this expression is equivalent to "i>0 ? 1.0 : 4.2".

	Guy Harris
	{seismo,ihnp4,allegra}!rlgvax!guy