\[x + \left(y - z\right) \cdot \frac{t - x}{a - z}\]
x + \left(y - z\right) \cdot \frac{t - x}{a - z}
double f(double x, double y, double z, double t, double a) {
        double r8443 = x;
        double r8444 = y;
        double r8445 = z;
        double r8446 = r8444 - r8445;
        double r8447 = t;
        double r8448 = r8447 - r8443;
        double r8449 = a;
        double r8450 = r8449 - r8445;
        double r8451 = r8448 / r8450;
        double r8452 = r8446 * r8451;
        double r8453 = r8443 + r8452;
        return r8453;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019191 +o rules:numerics
(FPCore (x y z t a)
  :name "Numeric.Signal:interpolate   from hsignal-0.2.7.1"
  (+ x (* (- y z) (/ (- t x) (- a z)))))

Backtrace

get-representation: Unknown representation #fLC
loop/data/pavpan/nightlies/herbie/interface2/src/points.rkt1224
prepare-points/data/pavpan/nightlies/herbie/interface2/src/points.rkt1460
setup-prog!34/data/pavpan/nightlies/herbie/interface2/src/mainloop.rkt670
run-improve43/data/pavpan/nightlies/herbie/interface2/src/mainloop.rkt3390
(unnamed)/opt/racket-7.0/collects/racket/private/more-scheme.rkt26128
run/opt/racket-7.0/share/pkgs/profile-lib/main.rkt392
profile-thunk16/opt/racket-7.0/share/pkgs/profile-lib/main.rkt90
(unnamed)/opt/racket-7.0/collects/racket/private/more-scheme.rkt26128