; Fieldtest mut-local #3 — evaluate the polynomial
;   p(x) = 2 x^3 - 3 x^2 + 5 x - 7
; at x = 2.5 by Horner's method, using a Float mut-var as the running
; accumulator and unrolling the four Horner steps as straight-line
; assigns.
;
; Why this fits mut-local's scope: the accumulator is a Float, the
; updates are straight-line (no iteration), and the mut form removes
; the four nested let-rebinds an LLM-author would otherwise write
; ("p1 = ..., p2 = p1*x + ..., p3 = p2*x + ...") — each rebind needing
; a fresh name. Reusing one name for the running accumulator is the
; natural shape, and mut supplies it.
;
; Hand-check (Horner): start with leading coeff 2.0, then for each
; lower coefficient do acc = acc * x + c:
;   2.0 * 2.5 + (-3) = 5.0 - 3 = 2.0
;   2.0 * 2.5 +   5  = 5.0 + 5 = 10.0
;   10.0 * 2.5 + (-7) = 25.0 - 7 = 18.0
; Expected stdout: 18  (Float 18.0 via %g; print drops the trailing
;   ".0" the same way it does for the Float fixture mut_sum_floats.ail.)

(module mut-local_3_horner

  (fn main
    (type (fn-type (params) (ret (con Unit)) (effects IO)))
    (params)
    (body
      (app print
        (mut
          (var acc (con Float) 2.0)
          (assign acc (app - (app * acc 2.5) 3.0))
          (assign acc (app + (app * acc 2.5) 5.0))
          (assign acc (app - (app * acc 2.5) 7.0))
          acc)))))