the kaleidoscope language is part of the LLVM intoroduction tutorial. given below is what a fibonacci number program would look like:

# Compute the x'th fibonacci number.
def fib(x)
  if x < 3 then
    1
  else
    fib(x-1)+fib(x-2)

# This expression will compute the 40th number.
fib(40)

it should also be possible to call math functions, like so:

extern sin(arg);
extern cos(arg);
extern atan2(arg1 arg2);

atan2(sin(.4), cos(42))

we will implement the scanner using flex as part of the compilers course at IIITH. a scanner takes as input, the program text, and processes it into tokens for the next stage of the compiler, parser. we use regular expressions to define each token type, and the associated action. flex is a scanner code generation tool that generates a C code for scanner, making our job a lot easier.

here is what the token would look like:

identifier: [a-zA-Z][a-zA-Z0-9]*
number:     [0-9.]+
comment:    #[^\n]*
symbol:     otherwise

see main.l for the scanner code. code can be compiled with make and lex.yy.c is the generated C code by flex.