README.md

Chapter 12: Floats

Table of Contents

1. Float

In this chapter, we add a floating point type and values.

You can also read this chapter in a linear Git revision history on the linear branch and compare it to the previous chapter.

Floats

Floating point values start with the flt type and compute IEEE754 64-bit arithmetic. Integer expressions auto-widen to floats when involved in a float expression.

flt f = 0.5;
int x = 2;
f = f+x;     // Auto-widen x to 2.0, result is 2.5
f = f+true;  // Since bools are just synonyms for integers 0,1 they auto-widen also

There is no corresponding way right now to round a flt back to an int:

int x = 3.14; // error

Here is Newton's method to a square root:

flt guess = arg;  // Initial guess is just argument
while( true ) {
    // Next guess from Newton's method
    flt next = (arg/guess + guess)/2;
    // Break if hit fixed point
    if( next == guess ) break;
    guess = next;
}
return guess;

When run with argument 2.0, produces 1.414213562373095.

Floating point operations have their own Nodes:

Node	Op
AddF, SubF, MulF, DivF	Basic binary FP ops
MinusF	Unary negate
EQF, LTF, LEF	FP compare operators

And their own section in the Type lattice:

Within the Type Lattice, we now add the following domain:

• Float type - Float values. The same shape as the Integer values, but floats with a TOP, BOT and constants