PEG:C++ Lesson 4 for Pascal Users

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C++ has a few operators that Pascal doesn't, but you don't need to know about them right now.

Arithmetic operators (+, -, *, and /) are the same in C++ as in Pascal, with one exception. In Pascal, / always yields a real, even if the operands were both integers and the quotient is an integer. In C++, dividing two integers always gives an integer (but if at least one operand is real then the result will be real too.) C++ also has the unary plus and minus (although unary plus is pretty useless...) We are able to do arithmetic with chars too, as they are stored as shortints.

div and mod: In C++, using ordinary division / on two integers has the same effect as using div in Pascal --- the fractional part is discarded and an integer results. In C++, the operator % is the same as mod in Pascal - taking two integer operands and returning an integer result. Again, we can use chars in C++ with these operations.

shl and shr, Pascal operators, find their equivalents as << and >> in C++. (These operators are also used for input and output, as you will see shortly.) Once again these operators work with chars too.

The operators <, <=, >, and >= are the same in Pascal and C++. The operator <> in Pascal is replaced with != in C++.

Now for the tricky part. Whereas in Pascal we wrote <left side> := <right side> for assignment, in C++ assignment is just a single equals sign (=). Now, the single equals sign is used in Pascal for testing if two values are equal. In C++, we use a double equals sign, ==.
For example:

x = 3;  //sets the value of x to 3
x := 3; //compile error
x == 3; //true if and only if x is 3
5 = 3;  //compile error
5 := 3; //compile error
5 == 3; //equal to false

(Yes, you are allowed to write a statement that does nothing but has a value, such as 5==3;, as in Pascal. But 5=3 is just plainly wrong, since we can't change the value of 5.)

When using the <, <=, >, >=, !=, ==, and = operators in C++, false is equivalent to 0, and true is equivalent to 1. If we assign an integer or a real to a bool, 0 is false, and anything else is true.

Pascal has the bit-string operators and, or, not, and xor. In C++ these are denoted by &, |, ~, and ^, respectively. However, C++ also has the operators &&, ||, and ! for logical and, or, and not, respectively. The difference is that these operators act on boolean values. So for example, 2&5 is zero since we take the binary representations 010 and 101, but 2&&5 is true, since both 2 and 5 are considered true.

The precedence of operators is as follows (operators on the same line have the same precedence, operators on a higher line have higher precedence):

+ - ! ~ (unary plus and minus)
* / %
+ - (binary plus and minus)
<< >>
< <= > >=
== !=

Both BEDMAS and NAXO are followed (yes, you can use parentheses, ( ), in C++ as well.)