macro "conj_elim" hp:ident hq:ident "from" h:ident : tactic =>
  `(tactic|(apply And.elim _ $h; intro $hp $hq))

macro "conj_intro" h:ident "from" hp:ident hq:ident : tactic =>
  `(tactic|(have $h : _∧_ := And.intro $hp $hq))

macro "disj_elim" hp:ident hq:ident "from" h:term:arg : tactic =>
  `(tactic|(refine Or.elim $h (fun $hp => ?_) (fun $hq => ?_)))

macro "disj_intro_left" h:ident "from" hp:ident q:term:arg : tactic =>
  `(tactic|(have $h : _∨($q) := Or.inl $hp))

macro "disj_intro_right" h:ident "from" p:term:arg hq:ident : tactic =>
  `(tactic|(have $h : ($p)∨_ := Or.inr $hq))

macro "impl_elim" hq:ident "from" hp:ident hpq:ident : tactic =>
  `(tactic|(have $hq := $hpq $hp))

namespace And
theorem elim' {P Q : Prop} {R : Sort} (h : P ∧ Q) (f : P → Q → R) : R :=
  And.elim f h
end And

variable (P Q R : Prop)

/- a hypothesis oriented proof -/
example (hp : P) (hpq : P → Q) : Q := by
  sorry

/- a goal oriented proof -/
example (hp : P) (hpq : P → Q) : Q := by
  sorry

/- a hypothesis oriented proof -/
example (hpq : P → Q) (hqr : Q → R) : P → R := by
  sorry

/- a goal oriented proof -/
example (hpq : P → Q) (hqr : Q → R) : P → R := by
  sorry

/- a hypothesis oriented proof -/
example ( h : P ∧ Q → R ) : ( P → Q → R ) := by
  sorry

/- a goal oriented proof -/
example ( h : P ∧ Q → R ) : ( P → Q → R ) := by
  sorry




/- a hypothesis oriented proof -/
example (h : P) : P ∨ Q := by
  sorry

/- a goal oriented proof -/
example (h : P) : P ∨ Q := by
  sorry


/- a hypothesis oriented proof -/
example (h : P ∨ Q) : Q ∨ P := by
  sorry

/- a goal oriented proof -/
example (h : P ∨ Q) : Q ∨ P := by
  sorry


/- a hypothesis oriented proof -/
example (h : P ∨ (Q ∨ R)) : (P ∨ Q) ∨ R := by
  sorry


/- a goal oriented proof -/
example (h : P ∨ (Q ∨ R)) : (P ∨ Q) ∨ R := by
  sorry