Cobra

My attempt at implementing a simple language using LLVM components in Rust.

Features:

• Python-like syntax
• Protoype declarations
• Functions
• Conditionals
• Loops
• Comments
• Error handling (soon)

Usage

# Run cobra program from file.
cargo run <filename>

# Run code interactively (parsing from stdin)
cargo run

Example

# fib.ks: Prints the fibonacci sequence up to n.
def fib(n)
  if n < 3 then
    1
  else
    fib(n-1) + fib(n-2);

fib(10);

$ cargo run fib.ks
Parse fib.ks.
[src/parser.rs:185] self.cur_tok() = Then
Parse 'def'
define double @fib(double %n) {
block:
  %fcmpult = fcmp ult double %n, 3.000000e+00 # check if n is less than 3 (if condition)
  br i1 %fcmpult, label %block5, label %block2 # if n is less than 3, branch to block5, otherwise to block2

block2:                                           ; preds = %block
  %fsub = fadd double %n, -1.000000e+00 # subtract 1 from n
  %call = call double @fib(double %fsub) # call function fib recursively
  %fsub3 = fadd double %n, -2.000000e+00 # subtract 2 from n
  %call4 = call double @fib(double %fsub3) # call function fib recursively
  %fadd = fadd double %call, %call4 # add result of the two recursive calls
  br label %block5

block5:                                           ; preds = %block, %block2
  %phi = phi double [ %fadd, %block2 ], [ 1.000000e+00, %block ] # if coming from block, return 1, otherwise return value from block2 (phi node, SSA)
  ret double %phi
}
define double @__anon_expr() {
block:
  %call = call double @fib(double 1.000000e+01) # call function fib with n = 10
  ret double %call # return value from function call
}
Evaluated to 55