# using Symata # when starting a stock Julia image
isymata() # when starting the precompiled-with Symata image

ClearAll()
[AtomQ(x), AtomQ(Sin(x)), AtomQ(1 + I * 2), AtomQ(2 / 3)]

[z * Sin(x +y), FullForm(z * Sin(x +y))]

a = z * Sin(x +y);
FullForm(a)

Head(a)

Clear(b, f, g, h, x);
b = f(g)(h)(x);
Head(b)

Head(f(g)(h))

Head(f(g))

[Head(f), Head(2), Head(Pi), Head(3.14), Head("abc"), Head(2/3), Head(1 + I)]

[a[0], a[1], a[2], a[2, 0], a[2, 1], a[2, 1, 0], a[2, 1, 1], a[2, 1, 2]]

Clear(a)
a = z * Sin(x + y) + z1 * Cos(x1 + y1)

FullForm(a)

Level(a, [0])

Level(a, [1])

Level(a, [2])

Level(a, [3])

Level(a, [4])

Level(a, [-1])

Level(a, [-2])

Level(a, [-3])

Level(a, [-4])

[Plus(1, 2, 3, 4), Times(1, 2, 3, 4)]

Clear(a, b, c, d, e)

a => b

[a, c, d, c] ./ (a => b)

Clear(f)
f(x_) := x^2
[f(2), f("word"), f(Newton)]

DownValues(f)

Clear(f)
f(x_Integer) := x^2
[f(2), f("word"), f(Newton)]

Clear(f)
f(x_`EvenQ`) := x
f(x_`OddQ`) := x^2
f(x_) := Sin(x)

[f(1), f(2), f(3), f(4), f(3 / 2), f(Newton), f(Pi)]

[EvenQ(2), EvenQ(3), OddQ(2), OddQ(3)]

[EvenQ(Newton), OddQ(Newton)]

Clear(f)
f(x_) := Sin(x)
f(x_`EvenQ`) := x
f(x_`OddQ`) := x^2
[f(1), f(2), f(3), f(4), f(3 / 2), f(Newton), f(Pi)]

DownValues(f)

FullForm(Sin(Pi + Pi))

Trace(True)
FullForm(Sin(Pi + Pi))

Trace(False);

VersionInfo()

InputForm(Now())