Merge pull request #491 from ChrisRackauckas-Claude/claude-fix-issue-490

Fix documentation examples for Symbolics.jl v7 compatibility

Author: ChrisRackauckas

docs/src/symbolics.md

@@ -18,7 +18,10 @@ A = LinearInterpolation(u, t)
 
 # Simple Expression
 ex = cos(τ) * A(τ)
-@test substitute(ex, Dict(τ => 0.5)) == cos(0.5) * A(0.5) # true
+
+# Build a function from the symbolic expression and evaluate it
+f_ex = build_function(ex, τ, expression = Val{false})
+@test f_ex(0.5) ≈ cos(0.5) * A(0.5) # true
 ```
 
 ### Symbolic Derivatives
@@ -31,12 +34,15 @@ ex1 = A(τ)
 # Derivative of interpolation
 ex2 = expand_derivatives(D(ex1))
 
-@test substitute(ex2, Dict(τ => 0.5)) == DataInterpolations.derivative(A, 0.5) # true
+# Build a function from the derivative expression and evaluate it
+f_deriv = build_function(ex2, τ, expression = Val{false})
+@test f_deriv(0.5) ≈ DataInterpolations.derivative(A, 0.5) # true
 
 # Higher Order Derivatives
 ex3 = expand_derivatives(D(D(A(τ))))
 
-@test substitute(ex3, Dict(τ => 0.5)) == DataInterpolations.derivative(A, 0.5, 2) # true
+f_deriv2 = build_function(ex3, τ, expression = Val{false})
+@test f_deriv2(0.5) ≈ DataInterpolations.derivative(A, 0.5, 2) # true
 ```
 
 ## Using with ModelingToolkit.jl