Issue 319 320 (#321)

* close #319; close  #320

* continue fixing  issue 320

* version bump

Author: jverzani

Project.toml

@@ -1,6 +1,6 @@
 name = "SymPy"
 uuid = "24249f21-da20-56a4-8eb1-6a02cf4ae2e6"
-version = "1.0.11"
+version = "1.0.12"
 
 [deps]
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"

src/lambdify.jl

@@ -32,11 +32,14 @@ function _piecewise(args...)
     ex
 end
 
+## Hack to avoid Expr(:call,  :*,2, x)  being  2x and  not  2*x
+__prod__(args...) =  prod(args)
+export __prod__
 
 fn_map = Dict(
               "Add" => :+,
               "Sub" => :-,
-              "Mul" => :*,
+              "Mul" => :__prod__,
               "Div" => :/,
               "Pow" => :^,
               "re"  => :real,
@@ -78,7 +81,7 @@ function walk_expression(ex; values=Dict(), fns=Dict())
         return walk_expression(rhs(ex), values=values, fns=fns)
     end
 
-    if fn == "Symbol"
+    if fn == "Symbol" || fn == "Dummy"
         str_ex = string(ex)
         return get(vals_map, str_ex, Symbol(str_ex))
     elseif fn in ["Integer" , "Float"]

src/mathfuns.jl

@@ -49,13 +49,13 @@ Base.log10(x::SymbolicObject) = log(10,x)
 ## use a pair for limit x=>0
 limit(x::SymbolicObject, xc::Pair, args...;kwargs...) = limit(x, xc[1], xc[2], args...;kwargs...)
 ## allow a function
-limit(f::Function, x::Sym, c;kwargs...) = limit(f(x), x, c;kwargs...)
-limit(f::Function, c;kwargs...) = limit(f, symbols("x"), c;kwargs...)
-
+limit(f::Function, x::Sym, c;kwargs...) = sympy.limit(f(x), x, c;kwargs...)
+limit(f::Function, c;kwargs...) = limit(f, sympy.Dummy("x"), c;kwargs...)
 
+## This is  type piracy  and a bad   idea
 function Base.diff(f::Function, n::Int=1)
-    x = symbols("x")
-    diff(f(x), x, n)
+    x = sympy.Dummy("x")
+    sympy.diff(f(x), x, n)
 end
 
 ## integrate(ex,a,b)
@@ -68,12 +68,12 @@ function integrate(ex::SymbolicObject, a::Number, b::Number)
     integrate(ex, (fs[1], a, b))
 end
 function integrate(f::Function, a::Number, b::Number)
-    x = symbols("x")
-    integrate(f(x), (x, a, b))
+    x = sympy.Dummy("x")
+    sympy.integrate(f(x), (x, a, b))
 end
 function integrate(f::Function)
-    x = symbols("x")
-    integrate(f(x))
+    x = sympy.Dummy("x")
+    sympy.integrate(f(x), x)
 end
 
 

test/tests.jl

@@ -569,6 +569,21 @@ end
     a = Sym(45)
     @test sind(a) == sin(PI/4)
 
+    # issue #319  with   use   of  Dummy, but
+    #  really  a  lambdify issue
+    dummy = sympy.Dummy
+    # Symbolic differentiation of functions
+    function D(f)
+        x = dummy("x")
+        lambdify(diff.(f(x), x), (x,))
+    end
+    @test D(t -> t^2)(1) == 2
+
+    # issue   #320  with integrate(f) when
+    # f  is consant
+    @test integrate(x -> 1, 0, 1)  == 1
+    @test limit(x->1,  x, 0) == 1
+    @test diff(x->1)  ==   0
 end
 
 @testset "generic programming, issue 223" begin