Functions

A major feature of the Ly language is its functions, which we will go over now.

Defining a function

Defining a function is simple:

<name>{<code>}

where <name> is a single character denoting the name of your function, and <code> is the body of your function.

Inside a function, code is executed just like a completely seperate Ly program. The only connection between a function and the main program is the input and output commands.

Instead of performing I/O from STDIN and STDOUT, a function manages I/O through the stack of the parent program.

An example function looks like this:

P{ns::[1-s%![l%!u;]p:l]}

This is a simple prime number checker program wrapped up in a function named P that takes a single number as a parameter and pushes either 0 or 1 to the stack depending on if the number passed was a prime or not.

NOTE: If you give a function the same name as an existing function or built-in instruction, the old function/instruction will be overwritten.

Calling functions

Calling functions is just as simple as creating them:

<name>

where <name> again is the name of the function.

The function is run like a normal program, with three differences:

• Whenever the function outputs, it is pushed to the stack of the parent program
• Whenever the function takes input, it is popped from the stack of the parent program
• There is no implicit input. When the parent stack is empty, taking input inside the function will yield 0.

Here is an example call of the prime number function:

p{i}

This will pop a number from the stack, and push 1 if it was prime and 0 otherwise.