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Combine terms in multiplication and addition #28

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Combine terms in multiplication and addition #28

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dfa26ad
Combine terms in multiplication and addition.
magistere Oct 24, 2013
357d5f2
Uncomment test that passes now
magistere Oct 25, 2013
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6 changes: 6 additions & 0 deletions src/symbolic.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -138,6 +138,9 @@ function simplify(::SymbolParameter{:+}, args)
# Special Case: simplify(:(+x)) == x
elseif length(args) == 1
return args[1]
# Special Case: simplify(:(x + x + x)) == 3*x
elseif all(args .== args[1])
return Expr(:call, :*, args[1], length(args))
else
(sum, sym_args) = sum_numeric_args(args)
args = sum==0 ? sym_args : [sum, sym_args]
Expand Down Expand Up @@ -171,6 +174,9 @@ function simplify(::SymbolParameter{:*}, args)
# Special Case: simplify(:(x * y * z * 0)) == 0
elseif any(args .== 0)
return 0
# Special Case: simplify(:(x * x * x * x)) == x^4
elseif all(args .== args[1])
return Expr(:call, :^, args[1], length(args))
else
(prod, sym_args) = mul_numeric_args(args)
args = prod==1 ? sym_args : [prod, sym_args]
Expand Down
10 changes: 6 additions & 4 deletions test/symbolic.jl
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Expand Up @@ -21,7 +21,7 @@
@test isequal(differentiate(:(tan(x)), :x), :(1 + tan(x)^2))
@test isequal(differentiate(:(exp(x)), :x), :(exp(x)))
@test isequal(differentiate(:(log(x)), :x), :(1 / x))
@test isequal(differentiate(:(sin(x) + sin(x)), :x), :(cos(x) + cos(x)))
@test isequal(differentiate(:(sin(x) + sin(x)), :x), :(2*cos(x)))
@test isequal(differentiate(:(sin(x) - cos(x)), :x), :(-(cos(x),*(-1,sin(x))))) # Simplify -(a, -(b)) => +(a, b)
@test isequal(differentiate(:(x * sin(x)), :x), :(sin(x) + x * cos(x)))
@test isequal(differentiate(:(x / sin(x)), :x), :((sin(x) - x * cos(x)) / (sin(x)^2)))
Expand All @@ -32,16 +32,14 @@
@test isequal(differentiate(:(x^n), :x), :(*(n, ^(x, -(n, 1)))))
@test isequal(differentiate(:(n^x), :x), :(*(^(n, x), log(n))))
@test isequal(differentiate(:(n^n), :x), 0)
@test isequal(differentiate(:(sin(x)^2), :x), :(2 * cos(x) * sin(x)))

#
# Multivariate Calculus
#

@test isequal(differentiate(:(sin(x) + sin(y)), [:x, :y]), [:(cos(x)), :(cos(y))])

# TODO: Get the generalized power rule right.
# @test isequal(differentiate(:(sin(x)^2), :x), :(2 * sin(x) * cos(x)))

#
# Strings instead of symbols
#
Expand Down Expand Up @@ -88,3 +86,7 @@ end
@test isequal(simplify(:(x*3)), :(*(3,x)))
@test isequal(simplify(:(x*3*4)), :(*(12,x)))
@test isequal(simplify(:(2*y*x*3)), :(*(6,y,x)))

@test isequal(simplify(:(x*x*x)), :(x^3))
@test isequal(simplify(:(x+x+x)), :(3*x))
@test isequal(simplify(:(f(x,y)+f(x,y))), :(2*f(x,y)))