56 lines
1.9 KiB
Plaintext
56 lines
1.9 KiB
Plaintext
; Fieldtest — Floats milestone, axis 3: NaN / Inf / is_nan handling.
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;
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; safe_div(a, b) returns a/b when b != 0; falls through to the IEEE
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; result otherwise. The fixture exercises four cases:
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; 1) 6.0 / 3.0 -> 2.0 (normal)
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; 2) 1.0 / 0.0 -> +inf (use is_nan to confirm finite-vs-NaN)
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; 3) 0.0 / 0.0 -> NaN (is_nan should report true)
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; 4) (- 1.0 1.0) / 0.0 -> NaN (subexpr drives same)
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;
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; classify(x) returns:
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; -1 if x is NaN
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; 0 if x is +inf or -inf (we test via x > <huge> / x < -<huge>)
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; 1 otherwise
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;
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; The subtle point: the IEEE-correct way to test for NaN is `is_nan`,
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; NOT `(== x x)` (which is false for NaN — but the LLM author who
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; reaches for `==` first will get the right answer by accident here,
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; only because the natural reading of the operator doesn't apply).
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; The DESIGN.md says explicitly to use `is_nan`.
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;
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; Expected stdout (one per line):
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; 2.0 ; 6/3
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; 1 ; classify(2.0) -> normal
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; inf ; 1/0
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; 0 ; classify(1/0) -> infinite
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; nan ; 0/0
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; -1 ; classify(0/0) -> NaN
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;
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; (`io/print_float` prints "%g\n", so inf prints as "inf", NaN as "nan".)
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(module floats_3_safe_division
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(fn classify
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(doc "-1=NaN, 0=infinite, 1=finite. Uses is_nan + abs > huge.")
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(type (fn-type (params (con Float)) (ret (con Int))))
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(params x)
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(body
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(if (app is_nan x)
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-1
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(if (app > x 1.0e308)
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0
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(if (app < x -1.0e308)
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0
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1)))))
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(fn main
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(type (fn-type (params) (ret (con Unit)) (effects IO)))
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(params)
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(body
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(seq (do io/print_float (app / 6.0 3.0))
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(seq (do io/print_int (app classify (app / 6.0 3.0)))
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(seq (do io/print_float (app / 1.0 0.0))
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(seq (do io/print_int (app classify (app / 1.0 0.0)))
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(seq (do io/print_float (app / 0.0 0.0))
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(do io/print_int (app classify (app / 0.0 0.0)))))))))))
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