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BigDecimal arithmetic: value-position + compare (Phase 1)

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bigdec values existed but +,-,*,/ and compare threw — the header even said
"arithmetic contagion is not modelled". Add the scale-aware engine on the
{unscaled, scale} pair (jbd-add/-sub/-mul/-div + comparison helpers) following
java.math.BigDecimal's rules: add/sub align to the larger scale, multiply adds
scales, divide gives the exact quotient at minimal scale or throws
ArithmeticException on a non-terminating expansion. Clojure contagion: a bigdec
mixed with an integer stays bigdec, a flonum operand wins (result is a double).

Wire it into the value-position shims only — jolt-add/-sub/-mul/-div (what
(reduce + bigs)/(apply * bigs) lower to) and compare — so the inlined native hot
path is untouched. A call-position (+ 1.5M 2.5M) still reaches the raw Chez op;
that needs the analyzer's :bigdec type (next).

Runtime .ss only, no re-mint. 13 JVM-certified corpus rows.
This commit is contained in:
Yogthos 2026-06-25 19:42:12 -04:00
parent ec9fde9e7e
commit bd7b75fb5d
2 changed files with 164 additions and 1 deletions
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13
test/chez/corpus.edn
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@ -1312,6 +1312,19 @@
{:suite "numbers / literal syntax" :label "bigint zero" :expected "0N" :actual "0N"}
{:suite "numbers / literal syntax" :label "bigdec suffix M" :expected "1.5M" :actual "1.5M"}
{:suite "numbers / literal syntax" :label "bigdec int M" :expected "0.0M" :actual "0.0M"}
{:suite "numbers / bigdec arithmetic" :label "add (value position)" :expected "4.0M" :actual "(reduce + [1.5M 2.5M])"}
{:suite "numbers / bigdec arithmetic" :label "add preserves max scale" :expected "\"4.00\"" :actual "(str (reduce + [1.50M 2.5M]))"}
{:suite "numbers / bigdec arithmetic" :label "add three" :expected "7.0M" :actual "(reduce + [1.5M 2.5M 3.0M])"}
{:suite "numbers / bigdec arithmetic" :label "subtract (apply)" :expected "3.5M" :actual "(apply - [5M 1.5M])"}
{:suite "numbers / bigdec arithmetic" :label "multiply adds scales" :expected "\"3.0000\"" :actual "(str (reduce * [1.50M 2.00M]))"}
{:suite "numbers / bigdec arithmetic" :label "long contagion stays bigdec" :expected "3.5M" :actual "(reduce + [1.5M 2])"}
{:suite "numbers / bigdec arithmetic" :label "double contagion -> double" :expected "3.5" :actual "(reduce + [1.5M 2.0])"}
{:suite "numbers / bigdec arithmetic" :label "exact divide minimal scale" :expected "\"0.25\"" :actual "(str (reduce / [1M 4M]))"}
{:suite "numbers / bigdec arithmetic" :label "exact divide whole" :expected "5M" :actual "(reduce / [10M 2M])"}
{:suite "numbers / bigdec arithmetic" :label "non-terminating divide throws" :expected ":nonterm" :actual "(try (reduce / [1M 3M]) (catch ArithmeticException _ :nonterm))"}
{:suite "numbers / bigdec arithmetic" :label "compare is scale-independent" :expected "0" :actual "(compare 1.0M 1.00M)"}
{:suite "numbers / bigdec arithmetic" :label "compare orders by value" :expected "-1" :actual "(compare 1.5M 2.5M)"}
{:suite "numbers / bigdec arithmetic" :label "sort uses bigdec compare" :expected "[1M 2M 3M]" :actual "(vec (sort [3M 1M 2M]))"}
{:suite "numbers / literal syntax" :label "ratio -> double" :expected "1/2" :actual "1/2"}
{:suite "numbers / literal syntax" :label "ratio 3/4" :expected "3/4" :actual "3/4"}
{:suite "numbers / literal syntax" :label "neg ratio" :expected "-1/2" :actual "-1/2"}