AST node for a definite integral: integral(e, v, lo, hi) in the grammar.
eval numerically integrates with composite Simpson's rule when low_limit and up_limit fold to concrete numbers. Step count is scaled by the interval length and the session precision. The fast path compiles the integrand to a Double => Double closure; the fallback evaluates the tree per step.
Value parameters
e
the integrand
low_limit
lower bound of integration
up_limit
upper bound of integration
v
the integration variable (binder -- excluded from children)
