8. Statements

8.1. Declaration

A variable declaration in VCalc has the following form:

<type> <id> = <expr>;

<type> is the type of the variable: int or vector.
<id> is the identifier of a variable.
<expr> is an expression.

Variables have a few properties:

cannot be used before being declared.
cannot be declared without initialisation.
cannot be declared more than once in a VCalc program.

Examples of valid declarations are:

int i = 9;
int j = 9 * 4 + 10;
vector k = i..j;

Examples of invalid declarations are:

int i;
vector j =;

Vectors may be initialized with any expression that returns a vector. For example, assigning a range to a vector v:

vector v = 1..10;
print(v);

prints the following:

[1 2 3 4 5 6 7 8 9 10]

8.2. Assignment

Variable assignment is similar to variable declaration but it allows variables to be assigned new values. An assignment in VCalc has the following form:

<id> = <expr>;

id is the identifier of an already declared variable.
expr is an expression.

There are a few new important points when dealing with assignments.

The size of a vector may change while the program is executing if a vector variable is assigned another value. For instance, the following sequence of statements is valid:
```
vector v = 1..10;
v = 1..1000;
```
You will have to allocate more memory to store the result of the assignment.
The type of the expression of the assignment must match the destination variable’s type. This is apparent for trying to assign vectors to a scalar. In the case of scalars being assigned to vectors, one might expect that we can use our extension policy to copy our scalar to every index of a newly created vector but the question is, how large is the new vector. Because that is indeterminable, this is not allowed. For example, the following sequence of statements is not valid:
```
int i = 1..3;
vector v = 1;
```
Many languages allow you to assign to vector indices, VCalc does not. For example, the following sequence of statements is not valid:
```
vector v = 1..3;
v[0] = 99;
```

8.3. Conditional

A conditional in VCalc has the following form:

if (<expr>)
  <statement-1>
  <statement-2>
  ...
  <statement-n>
fi;

expr is an expression. The body of the if statement is executed if and only if this expression evaluates to a non-zero value.
conditional conditions must evaluate to booleans, which means that vectors are not a valid condition. Remember, however, that integers undergo an implicit conversion to booleans.
statement-* is any type of statement except a declaration. This means there can be assignments, nested loops, nested conditionals, and prints. There does not have to be any statements in the conditional.

Clarification: Declarations in conditionals can lead to undefined values due to global scoping. (no-decl-cond)

8.4. Loops

A loop in VCalc has the following form:

loop (expr)
  <statement-1>
  <statement-2>
  ...
  <statement-n>
pool;

expr is an expression. The body of the loop statement is repeatedly evaluated as long as this expression is non-zero. The expression is evaluated prior to running the body similar to a C while loop.
Loop conditions must evaluate to booleans, which means that vectors are not a valid condition. Remember, however, that integers undergo an implicit conversion to booleans.
statement-* is any type of statement except a declaration. This means there can be assignments, nested loops, nested conditionals, and prints. There does not have to be any statements in the loop, but without side effects a loop will be infinite (unless it is never entered).

Clarification: Declarations in loops can lead to undefined or repeatedly defined values due to global scoping. (no-decl-loop)

8.5. Print

Print statements print the value of an expression followed by a newline. A print statement in VCalc has the following form:

print(<expr>);

expr is an expression.

For example, the input:

int i = 0;
loop (i < 5)
  print(i);
  i = i + 1;
pool;

should print:

The print statement must also be able to output vectors. All the elements of the vector are printed on a single line between the opening and closing brackets.

For example:

print(1..10);

prints the following:

[1 2 3 4 5 6 7 8 9 10]

The output of print is standardized to ensure everyone can pass everyone’s tests. Follow these specifications:

There must be a new line after each print statement’s printed value.
There must not be any trailing space after printed value and before the newline.
There must be an empty line at the end of your output.
There must not be spaces between the first and last number and the accompanying brackets in a vector.
There must be spaces between the numbers in a vector.
There must not be anything except spaces between the numbers in a vector.

Clarification: Empty input should result in empty output.
(empty-input)
Clarification: Empty vectors print only brackets.
(empty-vector)
Clarification: A vector with one value is only the brackets and
the value. (single-value-vector)