diff --git a/src/JuliaBUGS.jl b/src/JuliaBUGS.jl
index d56cfb599..6b2214f07 100644
--- a/src/JuliaBUGS.jl
+++ b/src/JuliaBUGS.jl
@@ -227,20 +227,20 @@ function compile(model_def::Expr, data, inits; is_transformed=true)
     check_input(data)
     check_input(inits)
 
-    scalars, array_sizes = program!(CollectVariables(), model_def, data)
-    has_new_val, transformed_variables = program!(
+    scalars, array_sizes = analyze_program(CollectVariables(), model_def, data)
+    has_new_val, transformed_variables = analyze_program(
         ConstantPropagation(scalars, array_sizes), model_def, data
     )
     while has_new_val
-        has_new_val, transformed_variables = program!(
+        has_new_val, transformed_variables = analyze_program(
             ConstantPropagation(false, transformed_variables), model_def, data
         )
     end
-    array_bitmap, transformed_variables = program!(
+    array_bitmap, transformed_variables = analyze_program(
         PostChecking(data, transformed_variables), model_def, data
     )
     merged_data = merge_with_coalescence(deepcopy(data), transformed_variables)
-    vars, array_sizes, array_bitmap, node_args, node_functions, dependencies = program!(
+    vars, array_sizes, array_bitmap, node_args, node_functions, dependencies = analyze_program(
         NodeFunctions(array_sizes, array_bitmap), model_def, merged_data
     )
     g = create_BUGSGraph(vars, node_args, node_functions, dependencies)
diff --git a/src/compiler_pass.jl b/src/compiler_pass.jl
index 02cfb1c52..59963f96d 100644
--- a/src/compiler_pass.jl
+++ b/src/compiler_pass.jl
@@ -1,87 +1,47 @@
-"""
-    CompilerPass
-
-Abstract supertype for all compiler passes. Concrete subtypes should store data needed and artifacts.
-"""
 abstract type CompilerPass end
 
-"""
-    program!(pass::CompilerPass, expr::Expr, env, vargs...)
-
-The entry point for a compiler pass, which traverses the AST and performs specific actions like assignment and for-loop processing.
-This function should be implemented for every concrete subtype of CompilerPass.
-
-Arguments:
-- pass: Instance of a concrete CompilerPass subtype.
-- expr: An Expr object representing the AST to be traversed.
-- env: A Dict object representing the environment.
-"""
-function program!(pass::CompilerPass, expr::Expr, env, vargs...)
+function analyze_program(pass::CompilerPass, expr::Expr, env, vargs...)
     for ex in expr.args
         if Meta.isexpr(ex, :(=))
-            assignment!(pass, ex, env, vargs...)
-        elseif MacroTools.@capture(ex, lhs_ ~ rhs_)
-            assignment!(pass, ex, env, vargs...)
+            analyze_assignment(pass, ex, env, vargs...)
+        elseif Meta.isexpr(ex, :call) && ex.args[1] == :(~)
+            analyze_assignment(pass, ex, env, vargs...)
         elseif Meta.isexpr(ex, :for)
-            for_loop!(pass, ex, env, vargs...)
+            analyze_for_loop(pass, ex, env, vargs...)
         else
-            error()
+            error("Unsupported expression in top level: $ex")
         end
     end
     return post_process(pass, expr, env, vargs...)
 end
 
-"""
-    for_loop!(pass::CompilerPass, expr, env, vargs...)
-
-Processes a for-loop from a traversed AST.
-"""
-function for_loop!(pass::CompilerPass, expr, env, vargs...)
-    loop_var = expr.args[1].args[1]
-    lb, ub = expr.args[1].args[2].args[2:end]
-    body = expr.args[2]
-
-    loop_var = Symbol(loop_var)
+function analyze_for_loop(pass::CompilerPass, expr, env, vargs...)
+    loop_var, lb, ub, body = decompose_for_expr(expr)
     lb = Int(evaluate(lb, env))
     ub = Int(evaluate(ub, env))
+
     for i in lb:ub
         for ex in body.args
             if Meta.isexpr(ex, :(=))
-                assignment!(pass, ex, merge(env, NamedTuple{(loop_var,)}((i,))), vargs...)
-            elseif ex.head == :call && ex.args[1] == :(~)
-                assignment!(pass, ex, merge(env, NamedTuple{(loop_var,)}((i,))), vargs...)
+                analyze_assignment(
+                    pass, ex, merge(env, NamedTuple{(loop_var,)}((i,))), vargs...
+                )
+            elseif Meta.isexpr(ex, :call) && ex.args[1] == :(~)
+                analyze_assignment(
+                    pass, ex, merge(env, NamedTuple{(loop_var,)}((i,))), vargs...
+                )
             elseif Meta.isexpr(ex, :for)
-                for_loop!(pass, ex, merge(env, NamedTuple{(loop_var,)}((i,))), vargs...)
+                analyze_for_loop(
+                    pass, ex, merge(env, NamedTuple{(loop_var,)}((i,))), vargs...
+                )
             else
-                error()
+                error("Unsupported expression in for loop body: $ex")
             end
         end
     end
 end
 
-"""
-    assignment!(pass::CompilerPass, expr::Expr, env, vargs...)
-
-Performs an assignment operation on a traversed AST. Should be implemented for every concrete subtype of CompilerPass.
-
-Arguments:
-- pass: Instance of a concrete CompilerPass subtype.
-- expr: An Expr object representing the assignment operation.
-- env: A Dict object representing the environment.
-"""
-function assignment!(::CompilerPass, expr::Expr, env, vargs...) end
-
-"""
-    post_process(pass::CompilerPass, expr, env, vargs...)
-
-Performs any post-processing necessary after traversing the AST. Should be implemented for every concrete subtype of CompilerPass.
-
-Arguments:
-- pass: Instance of a concrete CompilerPass subtype.
-- expr: An Expr object representing the traversed AST.
-- env: A Dict object representing the environment.
-"""
-function post_process(pass::CompilerPass, expr, env, vargs...) end
+function analyze_assignment end
 
 @enum VariableTypes begin
     Logical
@@ -367,7 +327,7 @@ is_resolved(::Array{Missing}) = false
 is_resolved(::Union{Symbol,Expr}) = false
 is_resolved(::Any) = false
 
-function assignment!(pass::CollectVariables, expr::Expr, env)
+function analyze_assignment(pass::CollectVariables, expr::Expr, env)
     if Meta.isexpr(expr, :(=))
         lhs_expr = expr.args[1]
     else # Expr(:call, :(~), ...)
@@ -456,7 +416,7 @@ function has_value(transformed_variables, v::Var)
     end
 end
 
-function assignment!(pass::ConstantPropagation, expr::Expr, env)
+function analyze_assignment(pass::ConstantPropagation, expr::Expr, env)
     if Meta.isexpr(expr, :(=)) && !should_skip_eval(expr.args[2])
         lhs = find_variables_on_lhs(expr.args[1], env)
 
@@ -520,7 +480,7 @@ function PostChecking(data, transformed_variables::Dict)
     )
 end
 
-function assignment!(pass::PostChecking, expr::Expr, env)
+function analyze_assignment(pass::PostChecking, expr::Expr, env)
     @inline set_value!(d::Dict, value, v::Scalar) = d[v.name] = value
     @inline set_value!(d::Dict, value, v::Var) = d[v.name][v.indices...] = value
     @inline get_value(d::Dict, v::Scalar) = d[v.name]
@@ -846,7 +806,7 @@ try_cast_to_int(x::Integer) = x
 try_cast_to_int(x::Real) = Int(x) # will error if !isinteger(x)
 try_cast_to_int(x) = x # catch other types, e.g. UnitRange, Colon
 
-function assignment!(pass::NodeFunctions, expr::Expr, env)
+function analyze_assignment(pass::NodeFunctions, expr::Expr, env)
     @capture(expr, lhs_expr_ ~ rhs_expr_) || @capture(expr, lhs_expr_ = rhs_expr_)
     var_type = Meta.isexpr(expr, :(=)) ? Logical : Stochastic
 
diff --git a/src/utils.jl b/src/utils.jl
index 5b4623f84..e1d520cb2 100644
--- a/src/utils.jl
+++ b/src/utils.jl
@@ -1,3 +1,17 @@
+"""
+    decompose_for_expr(expr::Expr)
+
+Decompose a for-loop expression into its components. The function returns four items: the 
+loop variable, the lower bound, the upper bound, and the body of the loop.
+"""
+@inline function decompose_for_expr(expr::Expr)
+    loop_var::Symbol = expr.args[1].args[1]
+    lb::Union{Int,Float64,Symbol,Expr} = expr.args[1].args[2].args[2]
+    ub::Union{Int,Float64,Symbol,Expr} = expr.args[1].args[2].args[3]
+    body::Expr = expr.args[2]
+    return loop_var, lb, ub, body
+end
+
 """
     _eval(expr, env)
 
diff --git a/test/methadone/methadone.jl b/test/methadone/methadone.jl
index be753f3f5..9cfb52348 100644
--- a/test/methadone/methadone.jl
+++ b/test/methadone/methadone.jl
@@ -87,10 +87,10 @@ end
 ##
 @time model = compile(model_def, data, inits);
 
-@time vars, array_sizes, transformed_variables, array_bitmap = JuliaBUGS.program!(
+@time vars, array_sizes, transformed_variables, array_bitmap = JuliaBUGS.analyze_program(
     JuliaBUGS.CollectVariables(), model_def, data
 );
 
-vars, array_sizes, array_bitmap, link_functions, node_args, node_functions, dependencies = JuliaBUGS.program!(
+vars, array_sizes, array_bitmap, link_functions, node_args, node_functions, dependencies = JuliaBUGS.analyze_program(
     JuliaBUGS.NodeFunctions(vars, array_sizes, array_bitmap), model_def, data
 );
diff --git a/test/passes.jl b/test/passes.jl
index 5c898b3f6..98e36ee0e 100644
--- a/test/passes.jl
+++ b/test/passes.jl
@@ -6,20 +6,20 @@
     end
     data = (b=1, e=[1, 2])
 
-    scalars, array_sizes = program!(CollectVariables(), model_def, data)
-    has_new_val, transformed_variables = program!(
+    scalars, array_sizes = analyze_program(CollectVariables(), model_def, data)
+    has_new_val, transformed_variables = analyze_program(
         ConstantPropagation(scalars, array_sizes), model_def, data
     )
     @test has_new_val == true
     @test transformed_variables[:a] == 2
 
-    has_new_val, transformed_variables = program!(
+    has_new_val, transformed_variables = analyze_program(
         ConstantPropagation(false, transformed_variables), model_def, data
     )
     @test has_new_val == true
     @test transformed_variables[:c] == 6
 
-    has_new_val, transformed_variables = program!(
+    has_new_val, transformed_variables = analyze_program(
         ConstantPropagation(false, transformed_variables), model_def, data
     )
     @test has_new_val == false
@@ -30,26 +30,26 @@ end
     data = JuliaBUGS.BUGSExamples.VOLUME_I[m].data
     inits = JuliaBUGS.BUGSExamples.VOLUME_I[m].inits[1]
 
-    scalars, array_sizes = program!(CollectVariables(), model_def, data)
+    scalars, array_sizes = analyze_program(CollectVariables(), model_def, data)
 
-    has_new_val, transformed_variables = program!(
+    has_new_val, transformed_variables = analyze_program(
         ConstantPropagation(scalars, array_sizes), model_def, data
     )
     @test has_new_val == true
     @test all(!ismissing, transformed_variables[:Y])
 
-    has_new_val, transformed_variables = program!(
+    has_new_val, transformed_variables = analyze_program(
         ConstantPropagation(false, transformed_variables), model_def, data
     )
 
     @test has_new_val == true
     @test all(!ismissing, transformed_variables[:dN])
 
-    array_bitmap, transformed_variables = program!(
+    array_bitmap, transformed_variables = analyze_program(
         PostChecking(data, transformed_variables), model_def, data
     )
 
-    vars, array_sizes, array_bitmap, node_args, node_functions, dependencies = program!(
+    vars, array_sizes, array_bitmap, node_args, node_functions, dependencies = analyze_program(
         NodeFunctions(array_sizes, array_bitmap),
         model_def,
         merge_with_coalescence(data, transformed_variables),
diff --git a/test/runtests.jl b/test/runtests.jl
index e2e065840..969982c25 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -23,7 +23,7 @@ using JuliaBUGS:
     MHFromPrior,
     NodeFunctions,
     PostChecking,
-    program!,
+    analyze_program,
     SimpleVarInfo,
     Stochastic,
     stochastic_inneighbors,
diff --git a/test/utils.jl b/test/utils.jl
index f14c1b9f5..13c1b565c 100644
--- a/test/utils.jl
+++ b/test/utils.jl
@@ -1,3 +1,24 @@
+@testset "Decompose for loop" begin
+    ex = MacroTools.@q for i in 1:3
+        x[i] = i
+        for j in 1:3
+            y[i, j] = i + j
+        end
+    end
+
+    loop_var, lb, ub, body = JuliaBUGS.decompose_for_expr(ex)
+    
+    @test loop_var == :i
+    @test lb == 1
+    @test ub == 3
+    @test body == MacroTools.@q begin
+        x[i] = i
+        for j in 1:3
+            y[i, j] = i + j
+        end
+    end
+end
+
 # Tests for `getparams`, using `Rats` model
 @testset "`getparams` with Rats" begin
     m = :rats