The C interpreter ought to be compiled before being used: you'll need a C compiler such as clang, gcc or the one coming with MS Visual Studio etc. Some compilers, such as clang, explicitly need to load math libraries when compiling.
The current folder contains all source files needed to compile the interpreter.
For example you could type, inside the [src/]:
clang -lm *.c -o awful
to create an executable for the Awful language (of course, add all compiler options you like). The executable awful can now be launched to execute the interpreter:
./awful
After launching the interpreter, a prompt will appear:
AWFUL - A Weird FUnctional Language
(c) 2023 by Paolo Caressa <github.com/pcaressa/awful>
[v.0.2312. Type 'help' for... guess what?]
niceful 1:
The prompt shows that the interpreter expects to receive a Niceful expression: type it and press ENTER. If the expression needs to span over multiple lines then add a final backslash to the line and the interpreter will ask for more, as in
niceful 1: let x = 10 \ This is a comment
niceful 2| in x ^ 2
100
niceful 3:
Text after a backslash will be ignored, so that one can use it also to insert comments.
The interpreter prints a progressive integer, after the prompt: it is useful when using batch files. To evaluate a file whose lines contain single expressions use batch FILENAME.
For example suppose the sample.nfl text file contains
\ Example of function application
(fun x: x + 1)(10)
19\
+\
21
Then, we could type
niceful 1: batch sample.nfl
11
40
niceful 2:
Inside a script one can use the bye and the batch directives, too.
The C interpreter is a single program, while Python provides two interpreters, one for Awful and one for Python. To switch to the Awful interpreter, use the command afwul as in
niceful 1: awful
Awful interpreter
awful 2:
To get back to the Niceful interpreter type niceful.
There are some more commands that can be typed instead of an expression: you can get them enumerated by the command help that prints the following short explanation:
Interactive mode: type the expression to evaluate on a single
line: to continue the expression on another line end it by
a backslash. Anything after the backslash will be ignored
(so you can use them as comments).
REPL commmands: type them instead of an expression, they are:
'awful': switch to Awful interpreter.
'batch FILENAME': the FILENAME text file is opened for
reading and each line of it is evaluated as a single
line typed in the interactive mode.
'bye' ends the session and closes the interpreter.
'help' prints this message.
'niceful': switch to Niceful interpreter.
'output': redirect output to terminal screen.
'output FILENAME': redirect output to file FILENAME (in append mode).
'prelude FILENAME ...' the FILENAME text file is opened for
reading and its lines are joined in a single line to
which the next input line is appended: the resulting
string is evaluated.
Warning: a preluded file cannot exceed 64Kbytes.
To leave the interpreter type bye.
These commands are explained also in the tutorial and in the language reference.
See the file ../doc/awful_intro_fl.md for a gentle introduction to the language and to the basic concepts in functional programming.
A short description of the language is in the ../README.md file in the root folder of the repository.