Getting Started with Fith
Learning Fith is very easy. The language is made to be as simple as possible, but there are still some things even experienced programmers may find strange.
Installing Fith
Fith and its tools are written in Python 3. To install them, run the following:
pip3 install fithlang
This will install the Fith suite as a python library, as well as install the following scripts:
- fithc: the fith compiler
- 5asm: the 5ir assembler
- 5vm: the 5vm itself
A Basic Example: Hello World
Write the following code in hello.fth:
`Hello,_World! prints
This should print the famous “Hello, World!” when compiled and run in the 5vm.
To compile and run the code, run the following in the terminal:
fithc -s -o hello.bin hello.fth
5vm hello.bin
Words in Fith
The fith language is based around the concept of words. Words are separated by any form of whitespase, and can be just about any non-whitespace charachters, with only a few exceptions.
The fith baselib defines some words for us, including the prints word used in the previous example. We can also define our own words like this:
:newword `This_is_a_word prints ;
newword
The definition is started with a colon and the word we are defining. We then give the words to execute, and end the definition with a semicolon.
The Stack
Fith words generally perform operations on something called the stack. The stack is a space in memory where we can push data to the top or pull data off the top. To push a value onto the stack, we just give that value. For example:
1 2 3 print cr print cr print
The word print pops the top value off the stack and prints it as a number. The word cr prints a new line. When we run this code, we should see the following output:
3
2
1
The numbers are printed in reverse, because the last number to be pushed is the first to be popped off the top.
Memory
It is not enough to deal with the stack. We also need to be able to store things in memory. For that, we have the words ! and @. The following code stores a value in a variable and prints it out:
42 answer !
answer @ print
Arithmetic
The baselib provides us with some arithmetic operations as well. Here are some examples:
1 2 + print
6 2 - print
12 3 / print
3 4 * print
1 2 < boolprint
3 4 > boolprint
5 5 = boolprint
Flow control
The last important aspect of fith is flow control. Fith has the special words if and else, but they may act differently from other languages you may have used. An example is below:
1 2 > if `1>2 else `1!>2 ; prints
1 2 < if `1<2 else `1!<2 ; prints
As you can see, the condition comes before the word if and the statement is closed with a semicolon.
Comments
Comments in fith start with the word /* and end with the word */. These must be written with space on both sides.