flint/examples/math.fl at main · programmersd21/flint · GitHub

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# math.fl -- the module you will reach for first.
#
#     ./flint examples/math.fl
#
# three things worth knowing about flint's numbers before reading on:
#
#   every number is a double. there is no integer type, so there is no
#   integer division and nothing to overflow.
#
#   only nil and false are falsy, so zero is true. `if x` does not mean
#   "if x is non-zero" and a loop condition is where that bites.
#
#   every number has a float implementation, so isfinite() is a real check
#   rather than a formality. dividing by zero gives inf, not an error.

import math

# the useful one: distance between two points
fn distance(x1, y1, x2, y2) {
    let dx = x2 - x1
    let dy = y2 - y1
    return math.sqrt(dx * dx + dy * dy)
}

print("distance (0,0) to (3,4): " + str(distance(0, 0, 3, 4)))
print("distance (1,1) to (4,5): " + str(distance(1, 1, 4, 5)))

# a circle
fn circle_area(radius) {
    return math.pi * radius * radius
}

print("area of r=5: " + str(circle_area(5)))

# trigonometry, in radians, because that is what the hardware does and
# degrees would be a conversion on every call for a display nicety
let angle = math.pi / 4
print("sin(pi/4) = " + str(math.sin(angle)))
print("cos(pi/4) = " + str(math.cos(angle)))

# round is half away from zero, which is the part people get caught by.
# c's nearby() rounds half to even, so 2.5 would come out as 2 there and 3
# here. documented in lib/math.fl because the alternative is a bug report.
print("round(0.5)  = " + str(math.round(0.5)))
print("round(2.5)  = " + str(math.round(2.5)))
print("round(-0.5) = " + str(math.round(-0.5)))

# cbrt is not pow(x, 1/3). that expression returns nan for a negative x,
# which is a fine answer from a function and a confusing one from a cube root.
print("cbrt(-27)      = " + str(math.cbrt(-27)))
print("pow(-27, 1/3)  = " + str(math.pow(-27, 1 / 3)))

# asking whether a number is a number is normal after a division
let good = 10 / 2
let bad = 1 / 0
let worse = 0 / 0

print("10/2  isfinite: " + str(math.isfinite(good)))
print("1/0   isinf:    " + str(math.isinf(bad)))
print("0/0   isnan:    " + str(math.isnan(worse)))

# a small numerical thing: the hypotenuse of a triangle, and the angle
# opposite a side. enough trig to be worth having.
fn hypotenuse(a, b) {
    return math.sqrt(a * a + b * b)
}

fn angle_opposite(a, b, c) {
    return math.acos((b * b + c * c - a * a) / (2 * b * c))
}

print("hypotenuse(3,4)     = " + str(hypotenuse(3, 4)))
print("angle opposite 5     = " + str(angle_opposite(5, 4, 3)) + " rad")
print("  ... in degrees     = " + str(angle_opposite(5, 4, 3) * 180 / math.pi))