fixed some issues with Decimals

notes/decimal_math_todo.md

@@ -0,0 +1,36 @@
+# Decimal Math TODO
+
+These stdlib math helpers currently accept `BigDecimal`, but some still use the temporary compatibility path
+
+`BigDecimal -> Real -> host math -> BigDecimal`
+
+instead of a native decimal implementation.
+
+## Still Using The Temporary Real Bridge
+
+- `sin(x)`
+- `cos(x)`
+- `tan(x)`
+- `asin(x)`
+- `acos(x)`
+- `atan(x)`
+- `sinh(x)`
+- `cosh(x)`
+- `tanh(x)`
+- `asinh(x)`
+- `acosh(x)`
+- `atanh(x)`
+- `exp(x)`
+- `ln(x)`
+- `log10(x)`
+- `log2(x)`
+- `sqrt(x)`
+- `pow(x, y)` when the decimal case is not reducible to an integral exponent
+
+## Already Native For Decimal
+
+- `abs(x)`
+- `floor(x)`
+- `ceil(x)`
+- `round(x)`
+- `pow(x, y)` with integral exponent `y`