ghrejogj^2

Out[2]

v={{2},{r}}

(Print["4"]; DoSomethingElse)

mF[x_]:=MatrixForm[x]

v//mF

v

v[[2]]

v[[2,1]]

v//TreeForm

E^(2./Sin[x^3/y])//TreeForm

exp=E^(2./Sin[x^3/y])

exp//FullForm

exp[[2,1]]

f@5
f[5]
5//f

?N

f[x_]:= x^2

f[{3,4}]

f[
{{3,4}}, 
{{3},{4}}
]

?Power

Attributes[Power]

Attributes[Plus]

Times[d,c]

times[a_,0]:=0
times[a_,1]:=a
times[a_,b_,c__]:=times[times[a,b],c]
times[a_,b_,c_]:= times[times[a,b],c]

times[2,3,4,5]

a=2,b=3,c=4,5

times[times[2,3],4,5]

a=times[2,3],b=4,c=5

?times

Clear[times]

?times

MatchQ

rule={a_^b_->b^a}

{x^2,3^x,x^x,x^y,3^2,a^b^c}/.rule

{3,4,2,1,0,45,xyz+t}/.{x_,y__,z___}->{z,y,x}

ReplaceList[{3,4,2,1,0,45,xyz+t}, {x_,y__,z___}->{{z},y,x}]//ColumnForm

?/.

g[{x___}]:=Length[{x}]

(* g[x__List]:=Length[x]*)

g[5]
g[{5}]
g[{}]
g[{1,2,3}]
g[1,2,3]

Clear[g]

g[{a_ w,b_},{c_,d_}]:=d^c^b^a

g[{Pi v,Sin[5]},{a,b}]
g[{Pi w,Sin[5]},{a,b}]
g[{w Pi,Sin[5]},{a,b}]

g[{
{a_,b_},
{c_,d_}
}]:= 
{{T[a],T[c]},
{T[b],T[d]}}

g[{{1,Zero},{4,5}}]

g[{
{a_,0},
{c_,d_}
}]:= 
Print["LowTri"]

?g

g[{
{a_,c_},
{c_,d_}
}]:= 
Print["Symm"]

g[{{1,c(b+d)},{b c + c d,5}}//Simplify]

{2,4,5,7,7,8,9}/.
{a___,b_,c_,d___}/;c==b+2->{b}

Clear[f]

f[a_,b_]/;b==a^2&&a<3:=b

f[2,4]