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cast                        Definition                       cast




The cast  operation ``coerces'' a variable from  one data type to
another.

There are two  reasons to cast a variable.  The  first is to con-
vert a  variable's data into  a form acceptable to  a given func-
tion.  For example, the function hhyyppoott takes two ddoouubbllees.  If the
variables lleegg_xx and lleegg_yy are ffllooaatts, the rules of C require that
they be cast automatically to ddoouubbllee.  If the compiler did not do
not do  this, hhyyppoott  would grab a  ddoouubbllee's worth of  memory: the
four bytes of your ffllooaatt,  plus four bytes of whatever happens to
be sitting on the stack.  The leads to results that are less than
totally accurate.

The other reason to cast a  variable is when you cast one type of
pointer to another.  For example,


        char *foo;
        int *bar;
        bar = (int *)foo;


Although ffoooo and  bbaarr are of the same length,  you would cast foo
in this instance to stop  the C compiler from complaining about a
type mismatch.

***** See Also *****

data formats, data types, definitions



























COHERENT Lexicon                                           Page 1

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