Hello world

Running SMART

For a simple first program, create a text file named hello.sm:

/*
  This is a comment 
*/
// This is a single-line comment
print("Hello, world!\n");

To run the program above, use:

smart hello.sm

This should give the output

Hello, world!

in your terminal.

Reading input

Now consider the program hello2.sm below:

string name := read_string("Name", 50);
print("Hello, ", name, "!\n");

The first statement causes SMART to prompt the user to enter a string with at most 50 characters (reading until whitespace), and store the result in a constant variable called name. Technically, there are no variables in SMART; instead, we have defined a function with no parameters called name. The print statement displays all of its arguments, in order. If we run this, though, we will get something like:

Hello, Enter the (string, length 50) value for Name : Alan Turing
Alan!

This is because SMART is very lazy, and does not compute a value for name until needed (in this case, when we try to print name, after printing the string “Hello, “.). A better version of this program would be:

string name := read_string("Name", 50);
compute(name);
print("Hello, ", name, "!\n");

where compute(name) forces SMART to compute the value for constant function name. If we run this program, we should obtain:

Enter the (string, length 50) value for Name : Alan Turing
Hello, Alan!