rodrigogiraoserrao · August 6, 2020 15:47
diff --git a/P5Phase2_2020.dyalog b/P5Phase2_2020.dyalog
 ⍝ PROBLEM 5.1 
 rr ← {
    (⎕IO ⎕ML ⎕WX) ← 0 1 3
    ⍝ Computes how much your investment is worth after cash flows and rate calculations.
    ⍝ Dyadic function expecting number vector on the left (deposits/withdrawals) and number vector on the right (corresponding rates).
    ⍝ At moment 1 you have r[1] ← ⍺[0] and at the subsequent moments you have r[n] ← ⍺[n-1] + r[n-1]×⍵[n-1].
    ⍝ Expanding the recurrence relation we can determine beforehand all expressions.
    ⍝ Assuming ⎕IO←0 and traditional mathematical notation,
    ⍝ r[1]←⍺[0], r[2]←⍺[1]+⍺[0]⍵[1], r[3]←⍺[2]+⍺[1]⍵[2]+⍺[0]⍵[2]⍵[1], r[4]←⍺[3]+⍺[2]⍵[3]+⍺[1]⍵[3]⍵[2]+⍺[0]⍵[3]⍵[2]⍵[1]
    ⍝ Returns a number.

    ⍝ This code manipulates triangular matrices as seen in https://aplcart.info/?q=extract%20triangular%20matrix#,
    ⍝  content I added to APL Cart, cf. https://github.com/abrudz/aplcart/pull/46
    _E ← {(⊢×∘.⍺⍺⍨∘⍳∘≢)⍵}  ⍝ Extract the lower/upper (strict?) triangular part of a matrix
    _M ← {(∘.⍺⍺⍨)⍵}        ⍝ Vector into rows (⊢) or columns (⊣) of a square matrix
    rt ← ×⍀ 1 + >_E ⊣_M ⍵  ⍝ Produce cumulative rates,
    a ← ≥_E ⊢_M ⍺          ⍝ expand amounts to proper shape
    +/ a × rt              ⍝ and sum them after multiplying.
 }

 ⍝ PROBLEM 5.2                                                
 ⍝ Computes the present value of an investment with future cash flows ⍺ at inflation rates ⍵.
 ⍝ Dyadic function expecting two vectors with the same length.
 ⍝ Returns a number.
 pv ← (1⊥×∘(×\1÷+∘1))
	⍝ PROBLEM 5.1
	rr ← {
	(⎕IO ⎕ML ⎕WX) ← 0 1 3
	⍝ Computes how much your investment is worth after cash flows and rate calculations.
	⍝ Dyadic function expecting number vector on the left (deposits/withdrawals) and number vector on the right (corresponding rates).
	⍝ At moment 1 you have r[1] ← ⍺[0] and at the subsequent moments you have r[n] ← ⍺[n-1] + r[n-1]×⍵[n-1].
	⍝ Expanding the recurrence relation we can determine beforehand all expressions.
	⍝ Assuming ⎕IO←0 and traditional mathematical notation,
	⍝ r[1]←⍺[0], r[2]←⍺[1]+⍺[0]⍵[1], r[3]←⍺[2]+⍺[1]⍵[2]+⍺[0]⍵[2]⍵[1], r[4]←⍺[3]+⍺[2]⍵[3]+⍺[1]⍵[3]⍵[2]+⍺[0]⍵[3]⍵[2]⍵[1]
	⍝ Returns a number.

	⍝ This code manipulates triangular matrices as seen in https://aplcart.info/?q=extract%20triangular%20matrix#,
	⍝ content I added to APL Cart, cf. https://github.com/abrudz/aplcart/pull/46
	_E ← {(⊢×∘.⍺⍺⍨∘⍳∘≢)⍵} ⍝ Extract the lower/upper (strict?) triangular part of a matrix
	_M ← {(∘.⍺⍺⍨)⍵} ⍝ Vector into rows (⊢) or columns (⊣) of a square matrix
	rt ← ×⍀ 1 + >_E ⊣_M ⍵ ⍝ Produce cumulative rates,
	a ← ≥_E ⊢_M ⍺ ⍝ expand amounts to proper shape
	+/ a × rt ⍝ and sum them after multiplying.
	}

	⍝ PROBLEM 5.2
	⍝ Computes the present value of an investment with future cash flows ⍺ at inflation rates ⍵.
	⍝ Dyadic function expecting two vectors with the same length.
	⍝ Returns a number.
	pv ← (1⊥×∘(×\1÷+∘1))