diff --git a/src/fexpr.jl b/src/fexpr.jl
new file mode 100644
index 0000000..efd337e
--- /dev/null
+++ b/src/fexpr.jl
@@ -0,0 +1,122 @@
+export unwrap_fun, wrap_fun, unwrap_head, wrap_head, unwrap_fcall, wrap_fcall
+################################################################
+"""
+    head, body = unwrap_fun(fexpr)
+    fcall, wherestack, body = unwrap_fun(fexpr,true)
+    f, args, wherestack, body = unwrap_fun(fexpr, true, true)
+
+Unwraps function expression.
+"""
+function unwrap_fun(expr::Expr)
+    if expr.head in (:function, :(=))
+        fexpr = expr
+    elseif expr.head == :block
+        fexpr = expr.args[2] # separate fexpr from block
+    else
+        error("Expression is not supported")
+    end
+
+    head = fexpr.args[1]
+    body = fexpr.args[2]
+    return head, body
+end
+
+function unwrap_fun(expr::Expr, should_unwrap_head::Bool)
+    if expr.head in (:function, :(=))
+        fexpr = expr
+    elseif expr.head == :block
+        fexpr = expr.args[2] # separate fexpr from block
+    else
+        error("Expression is not supported")
+    end
+
+    head = fexpr.args[1]
+    fcall, wherestack = unwrap_head(head)
+    body = fexpr.args[2]
+    return fcall, wherestack, body
+end
+
+function unwrap_fun(expr::Expr, should_unwrap_head::Bool, should_unwrap_fcall::Bool)
+    if expr.head in (:function, :(=))
+        fexpr = expr
+    elseif expr.head == :block
+        fexpr = expr.args[2] # separate fexpr from block
+    else
+        error("Expression is not supported")
+    end
+
+    head = fexpr.args[1]
+    fcall, wherestack = unwrap_head(head)
+    f, args = unwrap_fcall(fcall)
+
+    body = fexpr.args[2]
+    return f, args, wherestack, body
+end
+################################################################
+"""
+    fexpr = wrap_fun(f, args, wherestack, body)
+    fexpr = wrap_fun(fcall, wherestack, body)
+    fexpr = wrap_fun(head, body)
+    fexpr = wrap_fun(fexpr)
+
+Returns a function definition expression
+"""
+function wrap_fun(f, args, wherestack, body)
+    fcall = wrap_fcall(f, args)
+    head =  wrap_head(fcall, wherestack)
+    return Expr(:function, head, Expr(:block, body))
+end
+
+function wrap_fun(fcall, wherestack, body)
+    head =  wrap_head(fcall, wherestack)
+    return Expr(:function, head, Expr(:block, body))
+end
+
+function wrap_fun(head::Expr, body::Expr)
+    return Expr(:function, head, Expr(:block, body))
+end
+
+function wrap_fun(fexpr::Expr)
+    if fexpr.head in (:function, :(=))
+        return fexpr
+    elseif fexpr.head == :block
+        fexpr = fexpr.args[2] # separate fexpr from block
+        return fexpr
+    else
+        error("Expression is not supported")
+    end
+end
+
+################################################################
+function unwrap_head(head)
+    wherestack = Any[]
+    while head isa Expr && head.head == :where
+        push!(wherestack, head.args[2])
+        head = head.args[1]
+    end
+    fcall = head
+    fcall, wherestack
+end
+
+function wrap_head(fcall, wherestack)
+    for w in Iterators.reverse(wherestack)
+        fcall = Expr(:where, fcall, w)
+    end
+    head = fcall
+    return head
+end
+################################################################
+function unwrap_fcall(fcall::Expr)
+    if !(fcall.head == :call)
+        error("Expression is not supported")
+    end
+    f = fcall.args[1]
+    args = fcall.args[2:end]
+    return f, args
+end
+
+function wrap_fcall(f, args)
+    fcall = :($f($((args)...)))
+    return fcall
+end
+################################################################