diff --git a/src/SymEngine.jl b/src/SymEngine.jl
index c5d6693..8a1ebaa 100644
--- a/src/SymEngine.jl
+++ b/src/SymEngine.jl
@@ -21,8 +21,8 @@ const have_mpc = have_component("mpc")
 const libversion = get_libversion()
 
 include("exceptions.jl")
-include("types.jl")
 include("ctypes.jl")
+include("types.jl")
 include("decl.jl")
 include("display.jl")
 include("mathops.jl")
diff --git a/src/ctypes.jl b/src/ctypes.jl
index e043afc..d125d51 100644
--- a/src/ctypes.jl
+++ b/src/ctypes.jl
@@ -1,4 +1,21 @@
 # types from SymEngine to Julia
+
+## Basic
+## Hold a reference to a SymEngine object
+mutable struct Basic  <: Number
+    ptr::Ptr{Cvoid}
+    function Basic()
+        z = new(C_NULL)
+        ccall((:basic_new_stack, libsymengine), Nothing, (Ref{Basic}, ), z)
+        finalizer(basic_free, z)
+        return z
+    end
+    function Basic(v::Ptr{Cvoid})
+        z = new(v)
+        return z
+    end
+end
+
 ## CSetBasic
 mutable struct CSetBasic
     ptr::Ptr{Cvoid}
@@ -160,7 +177,7 @@ function CDenseMatrix(x::Array{T, 2}) where T
 end
 
 
-function Base.convert(::Type{Matrix}, x::CDenseMatrix) 
+function Base.convert(::Type{Matrix}, x::CDenseMatrix)
     m,n = Base.size(x)
     [x[i,j] for i in 1:m, j in 1:n]
 end
diff --git a/src/display.jl b/src/display.jl
index 4340c41..061a2fd 100644
--- a/src/display.jl
+++ b/src/display.jl
@@ -2,7 +2,7 @@
 function toString(b::SymbolicType)
     b = Basic(b)
     if b.ptr == C_NULL
-       error("Trying to print an uninitialized SymEngine Basic variable.")
+        return "<Unitialized Basic value>"
     end
     a = ccall((:basic_str_julia, libsymengine), Cstring, (Ref{Basic}, ), b)
     string = unsafe_string(a)
diff --git a/src/mathfuns.jl b/src/mathfuns.jl
index 81d074b..b282480 100644
--- a/src/mathfuns.jl
+++ b/src/mathfuns.jl
@@ -1,9 +1,17 @@
 using SpecialFunctions
 
-function IMPLEMENT_ONE_ARG_FUNC(meth, symnm; lib=:basic_)
+function IMPLEMENT_ONE_ARG_FUNC(modu, meth, symnm; lib=:basic_)
+    methbang = Symbol(meth, "!")
+    if isa(modu, Symbol)
+        meth = :($modu.$meth)
+    end
      @eval begin
         function ($meth)(b::SymbolicType)
             a = Basic()
+            ($methbang)(a,b)
+            a
+        end
+        function ($methbang)(a::Basic, b::SymbolicType)
             err_code = ccall(($(string(lib,symnm)), libsymengine), Cuint, (Ref{Basic}, Ref{Basic}), a, b)
             throw_if_error(err_code, $(string(meth)))
             return a
@@ -11,15 +19,25 @@ function IMPLEMENT_ONE_ARG_FUNC(meth, symnm; lib=:basic_)
     end
 end
 
-function IMPLEMENT_TWO_ARG_FUNC(meth, symnm; lib=:basic_)
+function IMPLEMENT_TWO_ARG_FUNC(modu, meth, symnm; lib=:basic_)
+    methbang = Symbol(meth, "!")
+    if isa(modu, Symbol)
+        meth = :($modu.$meth)
+    end
+
      @eval begin
         function ($meth)(b1::SymbolicType, b2::Number)
             a = Basic()
+            ($methbang)(a,b1,b2)
+            a
+        end
+         function ($methbang)(a::Basic, b1::SymbolicType, b2::Number)
             b1, b2 = promote(b1, b2)
             err_code = ccall(($(string(lib,symnm)), libsymengine), Cuint, (Ref{Basic}, Ref{Basic}, Ref{Basic}), a, b1, b2)
             throw_if_error(err_code, $(string(meth)))
             return a
         end
+
     end
 end
 
@@ -59,7 +77,7 @@ for (meth, libnm, modu) in [
                       (:floor, :floor, :Base)
                       ]
     eval(:(import $modu.$meth))
-    IMPLEMENT_ONE_ARG_FUNC(:($modu.$meth), libnm)
+    IMPLEMENT_ONE_ARG_FUNC(modu, meth, libnm)
 end
 
 for (meth, libnm, modu) in [
@@ -71,7 +89,7 @@ for (meth, libnm, modu) in [
     (:erfc, :erfc, :SpecialFunctions)
 ]
     eval(:(import $modu.$meth))
-    IMPLEMENT_ONE_ARG_FUNC(:($modu.$meth), libnm)
+    IMPLEMENT_ONE_ARG_FUNC(modu, meth, libnm)
 end
 
 for (meth, libnm, modu) in [
@@ -80,23 +98,31 @@ for (meth, libnm, modu) in [
     (:loggamma,:loggamma,:SpecialFunctions),
     ]
     eval(:(import $modu.$meth))
-    IMPLEMENT_TWO_ARG_FUNC(:($modu.$meth), libnm)
+    IMPLEMENT_TWO_ARG_FUNC(modu, meth, libnm)
 end
 
-Base.abs2(x::SymEngine.Basic) = abs(x)^2
-
+function abs2!(a::Basic, x::Basic)
+    abs!(a, x)
+    mul!(a, a, a)
+    a
+end
+function Base.abs2(x::Basic)
+    a = Basic()
+    abs2!(a, x)
+    a
+end
 
 
 if get_symbol(:basic_atan2) != C_NULL
     import Base.atan
-    IMPLEMENT_TWO_ARG_FUNC(:(Base.atan), :atan2)
+    IMPLEMENT_TWO_ARG_FUNC(:Base, :atan, :atan2)
 end
 
 # export not import
 for  (meth, libnm) in [
                        (:lambertw,:lambertw),   # in add-on packages, not base
                        ]
-    IMPLEMENT_ONE_ARG_FUNC(meth, libnm)
+    IMPLEMENT_ONE_ARG_FUNC(nothing, meth, libnm)
     eval(Expr(:export, meth))
 end
 
@@ -118,7 +144,7 @@ for (meth, libnm) in [(:gcd, :gcd),
                       (:mod, :mod_f),
                       ]
     eval(:(import Base.$meth))
-    IMPLEMENT_TWO_ARG_FUNC(:(Base.$meth), libnm, lib=:ntheory_)
+    IMPLEMENT_TWO_ARG_FUNC(:Base, meth, libnm; lib=:ntheory_)
 end
 
 Base.binomial(n::Basic, k::Number) = binomial(N(n), N(k))  #ntheory_binomial seems wrong
@@ -129,18 +155,18 @@ Base.factorial(n::SymbolicType, k) = factorial(N(n), N(k))
 ## but not (:fibonacci,:fibonacci), (:lucas, :lucas) (Basic type is not the signature)
 for (meth, libnm) in [(:nextprime,:nextprime)
                       ]
-    IMPLEMENT_ONE_ARG_FUNC(meth, libnm, lib=:ntheory_)
+    IMPLEMENT_ONE_ARG_FUNC(nothing, meth, libnm, lib=:ntheory_)
     eval(Expr(:export, meth))
 end
 
 "Return coefficient of `x^n` term, `x` a symbol"
-function coeff(b::Basic, x, n)
-    c = Basic()
+function coeff!(a::Basic, b::Basic, x, n)
     out = ccall((:basic_coeff, libsymengine), Nothing,
                 (Ref{Basic},Ref{Basic},Ref{Basic},Ref{Basic}),
-                c,b,Basic(x), Basic(n))
-    c
+                a,b,Basic(x), Basic(n))
+    a
 end
+coeff(b::Basic, x, n) = coeff!(Basic(), b, x, n)
 
 function Base.convert(::Type{CVecBasic}, x::Vector{T}) where T
     vec = CVecBasic()
diff --git a/src/mathops.jl b/src/mathops.jl
index da9815c..9a0611a 100644
--- a/src/mathops.jl
+++ b/src/mathops.jl
@@ -8,15 +8,20 @@ end
 
 
 ## main ops
-for (op, libnm) in ((:+, :add), (:-, :sub), (:*, :mul), (:/, :div), (://, :div), (:^, :pow))
+for (op, libnm) in ((:+, :add), (:-, :sub), (:*, :mul), (:/, :div), (:^, :pow))
     tup = (Base.Symbol("basic_$libnm"), libsymengine)
+    opbang = Symbol(libnm,:!)
     @eval begin
-        function ($op)(b1::Basic, b2::Basic)
-            a = Basic()
+        function ($opbang)(a::Basic, b1::Basic, b2::Basic)
             err_code = ccall($tup, Cuint, (Ref{Basic}, Ref{Basic}, Ref{Basic}), a, b1, b2)
             throw_if_error(err_code, $(string(libnm)))
             return a
         end
+        function ($op)(b1::Basic, b2::Basic)
+            a = Basic()
+            ($opbang)(a, b1, b2)
+            return a
+        end
         ($op)(b1::BasicType, b2::BasicType) = ($op)(Basic(b1), Basic(b2))
     end
 end
@@ -30,16 +35,20 @@ end
 # In contrast to other standard operations such as `+`, `*`, `-`, and `/`,
 # Julia doesn't implement a general fallback of `//` for `Number`s promoting
 # the input arguments. Thus, we implement this here explicitly.
+Base.:(//)(b1::SymbolicType, b2::SymbolicType) = b1 / b2
 Base.:(//)(b1::SymbolicType, b2::Number) = //(promote(b1, b2)...)
 Base.:(//)(b1::Number, b2::SymbolicType) = //(promote(b1, b2)...)
 
 
-function sum(v::CVecBasic)
-    a = Basic()
+function sum!(a::Basic, v::CVecBasic)
     err_code = ccall((:basic_add_vec, libsymengine), Cuint, (Ref{Basic}, Ptr{Cvoid}), a, v.ptr)
     throw_if_error(err_code, "add_vec")
     return a
 end
+function sum(v::CVecBasic)
+    a = Basic()
+    sum!(a, v)
+end
 
 +(b1::Basic, b2::Basic, b3::Basic, bs...) = sum(convert(CVecBasic, [b1, b2, b3, bs...]))
 +(b1::Basic, b2::Basic, b3, bs...) = +(Basic(b1), Basic(b2), Basic(b3), bs...)
@@ -51,12 +60,15 @@ end
 +(b1, b2, b3::Basic, bs...) = +(Basic(b1), Basic(b2), Basic(b3), bs...)
 
 
-function prod(v::CVecBasic)
-    a = Basic()
+function prod!(a::Basic, v::CVecBasic)
     err_code = ccall((:basic_mul_vec, libsymengine), Cuint, (Ref{Basic}, Ptr{Cvoid}), a, v.ptr)
     throw_if_error(err_code, "mul_vec")
     return a
 end
+function prod(v::CVecBasic)
+    a = Basic()
+    prod!(a, v)
+end
 
 *(b1::Basic, b2::Basic, b3::Basic, bs::Vararg{Number, N}) where {N} = prod(convert(CVecBasic, [b1, b2, b3, bs...]))
 *(b1::Basic, b2::Basic, b3::Number, bs::Vararg{Number, N}) where {N} = *(Basic(b1), Basic(b2), Basic(b3), bs...)
diff --git a/src/numerics.jl b/src/numerics.jl
index 52734fa..74ea3a3 100644
--- a/src/numerics.jl
+++ b/src/numerics.jl
@@ -131,6 +131,7 @@ end
 ## deprecate N(::BasicType)
 N(b::BasicType{T}) where {T} = N(convert(Basic, b), T)
 
+##  Conversions SymEngine -> Julia
 ## define convert(T, x) methods leveraging N() when needed
 function convert(::Type{Float64}, x::Basic)
     is_a_RealDouble(x) && return _convert(Cdouble, x)
@@ -170,11 +171,14 @@ Base.Real(x::Basic)    = convert(Real, x)
 
 
 ##  Rational --  p/q parts
-function as_numer_denom(x::Basic)
-    a, b = Basic(), Basic()
+function as_numer_denom!(a::Basic, b::Basic, x::Basic)
     ccall((:basic_as_numer_denom, libsymengine), Nothing, (Ref{Basic}, Ref{Basic}, Ref{Basic}), a, b, x)
     return a, b
 end
+function as_numer_denom(x::Basic)
+    a, b = Basic(), Basic()
+    as_numer_denom!(a,b,x)
+end
 
 as_numer_denom(x::BasicType) = as_numer_denom(Basic(x))
 denominator(x::SymbolicType) = as_numer_denom(x)[2]
diff --git a/src/simplify.jl b/src/simplify.jl
index f8a1954..656c829 100644
--- a/src/simplify.jl
+++ b/src/simplify.jl
@@ -1,4 +1,4 @@
-IMPLEMENT_ONE_ARG_FUNC(:expand, :expand)
+IMPLEMENT_ONE_ARG_FUNC(nothing, :expand, :expand)
 
 if get_symbol(:basic_cse) != C_NULL
     function cse(exprs...)
diff --git a/src/subs.jl b/src/subs.jl
index 9e23f8a..0d4d39e 100644
--- a/src/subs.jl
+++ b/src/subs.jl
@@ -18,17 +18,26 @@ subs(ex, x=>1, y=>1) # ditto
 """
 function subs(ex::T, var::S, val) where {T<:SymbolicType, S<:SymbolicType}
     s = Basic()
+    subs!(s, ex, var, val)
+end
+
+function subs!(s::Basic, ex::T, var::S, val) where {T<:SymbolicType, S<:SymbolicType}
     err_code = ccall((:basic_subs2, libsymengine), Cuint, (Ref{Basic}, Ref{Basic}, Ref{Basic}, Ref{Basic}), s, ex, var, val)
     throw_if_error(err_code, ex)
     return s
 end
+
 function subs(ex::T, d::CMapBasicBasic) where T<:SymbolicType
     s = Basic()
+    subs!(s, ex, d)
+end
+function subs!(s::Basic, ex::T, d::CMapBasicBasic) where T<:SymbolicType
     err_code = ccall((:basic_subs, libsymengine), Cuint, (Ref{Basic}, Ref{Basic}, Ptr{Cvoid}), s, ex, d.ptr)
     throw_if_error(err_code, ex)
     return s
 end
 
+
 subs(ex::T, d::AbstractDict) where {T<:SymbolicType} = subs(ex, CMapBasicBasic(d))
 subs(ex::T, y::Tuple{S, Any}) where {T <: SymbolicType, S<:SymbolicType} = subs(ex, y[1], y[2])
 subs(ex::T, y::Tuple{S, Any}, args...) where {T <: SymbolicType, S<:SymbolicType} = subs(subs(ex, y), args...)
diff --git a/src/types.jl b/src/types.jl
index 0d34bb3..86c6fb2 100644
--- a/src/types.jl
+++ b/src/types.jl
@@ -10,20 +10,6 @@
 ##
 ## To control dispatch, one might have `N(b::Basic) = N(BasicType(b))` and then define `N` for types of interest
 
-## Hold a reference to a SymEngine object
-mutable struct Basic  <: Number
-    ptr::Ptr{Cvoid}
-    function Basic()
-        z = new(C_NULL)
-        ccall((:basic_new_stack, libsymengine), Nothing, (Ref{Basic}, ), z)
-        finalizer(basic_free, z)
-        return z
-    end
-    function Basic(v::Ptr{Cvoid})
-        z = new(v)
-        return z
-    end
-end
 
 basic_free(b::Basic) = ccall((:basic_free_stack, libsymengine), Nothing, (Ref{Basic}, ), b)
 
@@ -293,20 +279,32 @@ end
 " Return free symbols in an expression as a `Set`"
 function free_symbols(ex::Basic)
     syms = CSetBasic()
-    ccall((:basic_free_symbols, libsymengine), Nothing, (Ref{Basic}, Ptr{Cvoid}), ex, syms.ptr)
+    free_symbols!(syms, ex)
     convert(Vector, syms)
 end
+function free_symbols!(syms::CSetBasic, ex::Basic)
+    ccall((:basic_free_symbols, libsymengine), Nothing, (Ref{Basic}, Ptr{Cvoid}), ex, syms.ptr)
+    syms
+end
+
 free_symbols(ex::BasicType) = free_symbols(Basic(ex))
+
 _flat(A) = mapreduce(x->isa(x,Array) ? _flat(x) : x, vcat, A, init=Basic[])  # from rosetta code example
+
 free_symbols(exs::Array{T}) where {T<:SymbolicType}  = unique(_flat([free_symbols(ex) for ex in exs]))
 free_symbols(exs::Tuple) =  unique(_flat([free_symbols(ex) for ex in exs]))
 
 "Return function symbols in an expression as a `Set`"
 function function_symbols(ex::Basic)
     syms = CSetBasic()
-    ccall((:basic_function_symbols, libsymengine), Nothing, (Ptr{Cvoid}, Ref{Basic}), syms.ptr, ex)
+    function_symbols!(syms, ex)
     convert(Vector, syms)
 end
+function function_symbols!(syms::CSetBasic, ex::Basic)
+    ccall((:basic_function_symbols, libsymengine), Nothing, (Ptr{Cvoid}, Ref{Basic}), syms.ptr, ex)
+    syms
+end
+
 function_symbols(ex::BasicType) = function_symbols(Basic(ex))
 function_symbols(exs::Array{T}) where {T<:SymbolicType} = unique(_flat([function_symbols(ex) for ex in exs]))
 function_symbols(exs::Tuple) = unique(_flat([function_symbols(ex) for ex in exs]))
@@ -322,23 +320,20 @@ end
 "Return arguments of a function call as a vector of `Basic` objects"
 function get_args(ex::Basic)
     args = CVecBasic()
-    ccall((:basic_get_args, libsymengine), Nothing, (Ref{Basic}, Ptr{Cvoid}), ex, args.ptr)
+    get_args!(args, ex)
     convert(Vector, args)
 end
 
+function get_args!(args::CVecBasic, ex::Basic)
+    ccall((:basic_get_args, libsymengine), Nothing, (Ref{Basic}, Ptr{Cvoid}), ex, args.ptr)
+end
+
 ## so that Dicts will work
 basic_hash(ex::Basic) = ccall((:basic_hash, libsymengine), UInt, (Ref{Basic}, ), ex)
 # similar definition as in Base for general objects
 Base.hash(ex::Basic, h::UInt) = Base.hash_uint(3h - basic_hash(ex))
 Base.hash(ex::BasicType, h::UInt) = hash(Basic(ex), h)
 
-function coeff(b::Basic, x::Basic, n::Basic)
-    c = Basic()
-    ccall((:basic_coeff, libsymengine), Nothing, (Ref{Basic}, Ref{Basic}, Ref{Basic}, Ref{Basic}), c, b, x, n)
-    return c
-end
-
-coeff(b::Basic, x::Basic) = coeff(b, x, one(Basic))
 
 function Serialization.serialize(s::Serialization.AbstractSerializer, m::Basic)
 	Serialization.serialize_type(s, typeof(m))
diff --git a/test/runtests.jl b/test/runtests.jl
index dc74e32..2336e45 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -19,7 +19,7 @@ let
     @vars w
 end
 @test_throws UndefVarError isdefined(w)
-@test_throws Exception show(Basic())
+@test repr(Basic()) == "<Unitialized Basic value>"
 
 # test @vars constructions
 @vars a, b[0:4], c(), d=>"D"
@@ -414,3 +414,5 @@ end
 	close(iobuf)
 	@test deserialized == data
 end
+
+VERSION >= v"1.9.0" && include("test-allocations.jl")
diff --git a/test/test-allocations.jl b/test/test-allocations.jl
new file mode 100644
index 0000000..1f67dce
--- /dev/null
+++ b/test/test-allocations.jl
@@ -0,0 +1,18 @@
+# test for allocations
+@vars x y
+a = Basic()
+@testset "non-allocating(ish) methods" begin
+    sin(x), cos(x), abs(x)
+    x^x, x + x, x*x, x-x, x/x # warm up
+
+    @test (@allocations SymEngine.sin!(a,x)) == 0
+    @test (@allocations SymEngine.cos!(a,x)) == 0
+    @test (@allocations SymEngine.pow!(a,x,x)) == 0
+
+    # still allocates 1 (or 2)
+    @test (@allocations SymEngine.add!(a,x,y)) < (@allocations x+y)
+    @test (@allocations SymEngine.sub!(a,x,y)) < (@allocations x-y)
+    @test (@allocations SymEngine.mul!(a,x,y)) < (@allocations x*y)
+    @test (@allocations SymEngine.div!(a,x,y)) < (@allocations x/y)
+    @test (@allocations SymEngine.abs2!(a,x)) < (@allocations abs2(x))
+end