sx/examples/0168-types-integral-float-to-int.sx

// Unified float→int narrowing rule (F0.11), POSITIVE side: an INTEGRAL float
// flowing into an integer-typed binding FOLDS to its integer — the same
// `floatToIntExact` rule an array dimension / `$K: Count` already uses — across
// all FIVE sites: a typed LOCAL, a struct FIELD default, a typed module CONST, a
// function PARAM default, and an array DIMENSION. It folds whether written as a
// float LITERAL (`4.0`), an INT-const-EXPRESSION (`M + 2.0`, with `M :: 2`), a
// FLOAT-const-LEAF expression whose sum is integral (`F + 1.5`, with
// `F : f64 : 2.5`, = 4.0) — including such a float-const-leaf expression driving
// an array dimension directly, through a const, or via a type alias — a builtin
// FLOAT numeric-limit leaf in an integral expression (`f64.max - f64.max` = 0),
// and an integral float `%` (`6.0 % 4.0` = 2). The compile-time float evaluator
// is at parity with the integer one, so integer numeric-limit accessors (`s8.max`,
// `[u8.max]` count) keep folding through the shared int folder, unregressed.
// The escape hatch (`xx` / `cast`) still TRUNCATES any float, integral or not —
// including a non-integral const expression (`xx (M + 0.5)` / `xx (F + 0.25)`).
//
// Companion to the negative example 1146 (non-integral floats error).
// Regression (issue 0095): a typed local/param/field silently truncated a float
// initializer (`y : s64 = 1.5` → 1) with no diagnostic; a non-integral const
// EXPRESSION (`M + 0.5`) and a non-integral float-const-LEAF expression
// (`F + 0.25`) truncated even when written through an int binding; the rule now
// folds an integral float (literal, int-const expr, or float-const leaf) and
// rejects a non-integral one.
#import "modules/std.sx";

M :: 2;          // int module const, for the INT-const-EXPRESSION cases
F : f64 : 2.5;   // float module const, for the FLOAT-const-LEAF cases

Box :: struct {
    n  : s64 = 4.0;       // integral float field default → folds to 4
    ne : s64 = M + 2.0;   // integral int-const-EXPR field default → folds to 4
    nf : s64 = F + 1.5;   // integral float-const-LEAF field default → folds to 4
}

withDefault :: (x : s64 = 6.0)     -> s64 { return x; }   // param default → 6
withFlt     :: (x : s64 = F + 1.5) -> s64 { return x; }   // float-const-leaf param default → 4

K  : s64 : 8.0;          // integral float module const → folds to 8
KF : s64 : F + 1.5;      // integral float-const-LEAF module const → folds to 4

ArrFE :: [F + 1.5]s64;   // array-dim type ALIAS over a float-const-leaf expr → [4]s64
                         // (the stateless registration path must agree with the
                         //  direct form `a : [F + 1.5]s64` below — issue 0083).

main :: () {
    // Typed local: integral float folds (literal + int-const expr + float-const leaf).
    z : s64 = 4.0;
    ze : s64 = M + 2.0;
    zf : s64 = F + 1.5;
    print("local={} localExpr={} localFlt={}\n", z, ze, zf);

    // Negative integral float folds to its (negative) integer.
    neg : s64 = -2.0;
    print("neg={}\n", neg);

    // Struct field defaults fold (literal + int-const expr + float-const leaf).
    b := Box.{};
    print("field={} fieldExpr={} fieldFlt={}\n", b.n, b.ne, b.nf);

    // Param defaults fold.
    print("param={} paramFlt={}\n", withDefault(), withFlt());

    // Module consts fold (and an integral float const can drive an array dim: len 8).
    a : [K]s64 = ---;
    print("const={} constFlt={} len={}\n", K, KF, a.len);

    // Array DIMENSION — the fifth site joins the unified rule: an integral
    // float-const-leaf expression folds to a count whether written DIRECTLY
    // (`[F + 1.5]` → 4), THROUGH a float-expr const (`[KF]`, KF = F + 1.5 = 4),
    // or via a type ALIAS (`ArrFE`, the stateless path agreeing with the direct).
    ad : [F + 1.5]s64 = ---;
    ak : [KF]s64 = ---;
    aa : ArrFE = ---;
    print("dim.direct={} dim.const={} dim.alias={}\n", ad.len, ak.len, aa.len);

    // Numeric-limit float leaf in an expression: an INTEGRAL result folds (the
    // compile-time float evaluator is at parity with the integer one — a
    // `f64`/`f32` `.max`/`.min`/`.epsilon`/… leaf is recognised inside an
    // expression, not only as a direct value). `f64.max - f64.max` = 0.0 → 0.
    lim : s64 = f64.max - f64.max;
    // Integral float `%` (parity with int `%`): `6.0 % 4.0` = 2.0 → 2.
    fm : s64 = 6.0 % 4.0;
    print("limit={} fmod={}\n", lim, fm);

    // Integer numeric-limit accessors (NL.1) are unregressed by the float-leaf
    // parity work: they still fold at a binding (`s8.max` = 127) and as an array
    // dimension count (`[u8.max]` = len 255), through the SAME int folder.
    il : s64 = s8.max;
    iarr : [u8.max]s64 = ---;
    print("intlimit={} intcount={}\n", il, iarr.len);

    // Explicit escape: `xx` / `cast` always truncate, integral or not —
    // including a non-integral const EXPRESSION (`xx (M + 0.5)` → 2), a
    // non-integral float-const-LEAF expression (`xx (F + 0.25)` → 2), a
    // non-integral numeric-limit expr (`xx (f64.true_min + 0.5)` → 0), and a
    // non-integral float `%` (`xx (5.5 % 2.0)` → 1).
    e : s64 = xx 4.9;
    c : s64 = cast(s64) 1.5;
    xc : s64 = xx (M + 0.5);
    xf : s64 = xx (F + 0.25);
    xl : s64 = xx (f64.true_min + 0.5);
    xm : s64 = xx (5.5 % 2.0);
    print("xx={} cast={} xxExpr={} xxFlt={} xxLimit={} xxMod={}\n", e, c, xc, xf, xl, xm);
}