Add comments and whitespace for clarity

Author: mikeingold

src/integral.jl

@@ -44,16 +44,20 @@ function _integral(
         FP::Type{T} = Float64,
         diff_method::DM = _default_method(geometry)
 ) where {DM <: DifferentiationMethod, T <: AbstractFloat}
-    # Pass through to dim-specific workers in next section of this file
     N = Meshes.paramdim(geometry)
+
+    # Implementation depends on number of parametric dimensions over which to integrate
     if N == 1
         integrand(t) = f(geometry(t)) * differential(geometry, (t,), diff_method)
         return QuadGK.quadgk(integrand, zero(FP), one(FP); rule.kwargs...)[1]
     elseif N == 2
+        # Issue deprecation warning
         Base.depwarn("Use `HAdaptiveCubature` instead of nested `GaussKronrod` rules.", :integral)
+
+        # Nested integration
         integrand(u, v) = f(geometry(u, v)) * differential(geometry, (u, v), diff_method)
-        ∫₁(v) = QuadGK.quadgk(u -> integrand(u, v), zero(FP), one(FP); rule.kwargs...)[1]
-        return QuadGK.quadgk(v -> ∫₁(v), zero(FP), one(FP); rule.kwargs...)[1]
+        ∫(v) = QuadGK.quadgk(u -> integrand(u, v), zero(FP), one(FP); rule.kwargs...)[1]
+        return QuadGK.quadgk(∫, zero(FP), one(FP); rule.kwargs...)[1]
     else
         _error_unsupported_combination("geometry with more than two parametric dimensions",
             "GaussKronrod")