Exception for (if (< a b) (/ (sqrt (* (* (* (+ c (+ b a)) (- a (- c b))) (+ a (- c b))) (+ c (- b a)))) 4) (/ (sqrt (* (* (* (+ c (+ a b)) (- b (- c a))) (+ b (- c a))) (+ c (- a b)))) 4))

Math

\[\begin{array}{l} \mathbf{if}\;a \lt b:\\ \;\;\;\;\frac{\sqrt{\left(\left(\left(c + \left(b + a\right)\right) \cdot \left(a - \left(c - b\right)\right)\right) \cdot \left(a + \left(c - b\right)\right)\right) \cdot \left(c + \left(b - a\right)\right)}}{4}\\ \mathbf{else}:\\ \;\;\;\;\frac{\sqrt{\left(\left(\left(c + \left(a + b\right)\right) \cdot \left(b - \left(c - a\right)\right)\right) \cdot \left(b + \left(c - a\right)\right)\right) \cdot \left(c + \left(a - b\right)\right)}}{4}\\ \end{array}\]

C

double code(double a, double b, double c) {
	double VAR;
	if ((a < b)) {
		VAR = ((double) (((double) sqrt(((double) (((double) (((double) (((double) (c + ((double) (b + a)))) * ((double) (a - ((double) (c - b)))))) * ((double) (a + ((double) (c - b)))))) * ((double) (c + ((double) (b - a)))))))) / 4.0));
	} else {
		VAR = ((double) (((double) sqrt(((double) (((double) (((double) (((double) (c + ((double) (a + b)))) * ((double) (b - ((double) (c - a)))))) * ((double) (b + ((double) (c - a)))))) * ((double) (c + ((double) (a - b)))))))) / 4.0));
	}
	return VAR;
}

Reproduce

herbie shell --seed 2020152 
(FPCore (a b c)
  :name "(if (< a b) (/ (sqrt (* (* (* (+ c (+ b a)) (- a (- c b))) (+ a (- c b))) (+ c (- b a)))) 4) (/ (sqrt (* (* (* (+ c (+ a b)) (- b (- c a))) (+ b (- c a))) (+ c (- a b)))) 4))"
  :precision binary64
  (if (< a b) (/ (sqrt (* (* (* (+ c (+ b a)) (- a (- c b))) (+ a (- c b))) (+ c (- b a)))) 4.0) (/ (sqrt (* (* (* (+ c (+ a b)) (- b (- c a))) (+ b (- c a))) (+ c (- a b)))) 4.0)))