using Symata

[2x + 1, 2 * x + 1, 2 * 3, Cos(x) * Sin(x)]

# a = 1
  b = 2

[a,b]

[a,b,c]

[
    a
    c + d
    "cat"
    Expand((x+y)^2)
]

f(x)

e1 = (1,2,a+b)

e2 = (1,
      2,
      a+b)

e3  = begin
     1;
     2;
     a+b
end

e1 == e2 == e3

f % list

f % [a,b,c]

x .%  y

f .% g(1,2)

[Rule(a,b), a => b , a ⇒ b]

[RuleDelayed(a,b),  a .> b]

[a, x^2, b^3, (a+b)^3]  ./ ( x_^n_ => g([n],x))

f(x_, y__) := [x,[y]]
f(1,2,3,4)

[
MatchQ([a, a, b, (a + b)^3, c, c, c], [a..., b, _^3... , c...])
MatchQ([a, a, (a + b)^3, c, c, c], [a..., b, _^3... , c...])
]

ClearAll(f)
f(x_...) := x

f(3,3,3,3)

[
    MatchQ([1,2,3], [Repeated(_Integer,2)])
    MatchQ([1,2,3], [Repeated(_Integer,3)])
]

MatchQ([], [RepeatedNull(_Integer)])

ClearAll(f, a, b)

f(x_, y_:a, z_:b) := [x,y,z]

[
 f(1) == [1,a,b]
 f(1,2) == [1,2,b]
 f(1,2,3) == [1,2,3]
]

ClearAll(g,a,b)

b^b  ./  (a::(_^_) => g(a))

countprimes = Count(_`PrimeQ`)  # We use the curried form of Count
countprimes(Range(100))

p = _`J( x ->  -1 < x < 1 )`

[
MatchQ(0, p),
MatchQ(.5, p),
MatchQ(-1/2, p),
MatchQ(-1, p)
]

ClearAll(f)

f(x_, x_ | y_String) := [x, y]

[ f(2,2) , f(2,"cat"), f(2, 3)]


[
MatchQ( -2 , Condition(x_ , x < 0))
MatchQ(  2 , Condition(x_ , x < 0))
]

ClearAll(y)

ReplaceAll([1, 2, 3, "cat"], x_Integer => Condition(y, x > 2))

ClearAll(f)

f(x_) :=  Condition(x^2, x > 3)

[f(2), f(4)]

VersionInfo()

InputForm(Now())