forcing evaluation order (was "Expression Sequencing Query")

Tom Stockfisch tps at sdchem.UUCP
Thu Oct 23 06:09:34 AEST 1986

In article <2809 at watmath.UUCP> rbutterworth at watmath.UUCP (Ray Butterworth) writes:
>> The ANSI C draft standard provides the unary plus operator for coercing
>> evaluation order.  Thus
>>     a = +(b + c) + +(d) ;
>> should force the sum of b+c to be calculated and added to d....
>Does X3J11 (or any other C "standard") say anything about the
>order of evaluation of (possibly redundant) cast expressions?
>e.g.      ( ((double)(a+b)) + ((double)(c+d)) )
>where a, b, c, and d may or may not be type (double)?
>It would certainly be prettier than the unary " +" operator,
>and certainly more obvious that the programmer really did want
>the given grouping.

I find the c a s t much harder to read.
I much prefer to have all alphanumeric
objects in an expression be variables,
and all operators to be
non-alphanumeric.  In addition, for
numeric expressions, the fewer the
parentheses the better, since they tend
to be profuse.  I don't understand why
you think the intent is clearer with the
cast.  The sole purpose (I think) of
unary plus is to force evaluation order,
whereas casts are normally used for type
conversion.  In your example, if a, b,
c, and d were all doubles, I would be
very confused about the purpose of c a s
t i n g them to double.

-- Tom Stockfisch, UCSD Chemistry

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