Built-in Functions

General Abilities of a HCL Program

This part will discuss about the various statements and native functions of HCL.

General IO

HCL has two statements for printing to standard output:

1. The print statement: prints the given expression to the STDOUT without newline.

2. The println statement: prints the given expression to the STDOUT along with newline.

Both the statements has to be used in the following format:

print <expression>;
# or
println <expression>;

For input, the input(1) function is used. It is of the format:

input(prompt);

where prompt is a string which is prompted during input. This function returns a string of user's input.

Datatype Conversion

The input(1) function always return the result as a string. To convert it into other types, the following functions are used:

1. num(1): This function converts a given string to a valid number

2. bool(1): This function converts a given string to a boolean value

Other than these, there is also a need to convert the num and bool datatypes to string. The native function str(1) converts the values in the above datatypes into string.

Formatted strings

More often, you will have to interpolate a string with various values generated during programming. For such cases, the native function fmt() function is used. It is of the form

fmt(fmtString, subs...)

Where: fmtString is a string containing string with format specifiers and subs... is a Variadic argument whose length depend upon the specifiers in the fmtString.

For example, here is a simple program to greet user(the same greet.hcl program:

# Program to Input and print username

let name := input("Enter you name: ");
println fmt("Hi, %s!", name);

Here, the fmt() function replaces the "%s" in the string with the value stored in the variable name. The format string specifiers are the same as in Java.