2024-05-12 10:38:39 +00:00
|
|
|
|
---
|
|
|
|
|
|
language: APL
|
|
|
|
|
|
contributors:
|
|
|
|
|
|
- ["nooodl", "https://github.com/nooodl"]
|
|
|
|
|
|
filename: learnapl.apl
|
|
|
|
|
|
---
|
|
|
|
|
|
|
|
|
|
|
|
```apl
|
2024-05-12 10:34:52 +00:00
|
|
|
|
⍝ Comments in APL are prefixed by ⍝.
|
|
|
|
|
|
|
|
|
|
|
|
⍝ A list of numbers. (¯ is negative)
|
|
|
|
|
|
2 3e7 ¯4 50.3
|
|
|
|
|
|
|
|
|
|
|
|
⍝ An expression, showing some functions. In APL, there's
|
|
|
|
|
|
⍝ no order of operations: everything is parsed right-to-
|
|
|
|
|
|
⍝ left. This is equal to 5 + (4 × (2 ÷ (5 - 3))) = 9:
|
|
|
|
|
|
5 + 4 × 2 ÷ 5 - 3 ⍝ 9
|
|
|
|
|
|
|
|
|
|
|
|
⍝ These functions work on lists, too:
|
|
|
|
|
|
1 2 3 4 × 5 ⍝ 5 10 15 20
|
|
|
|
|
|
1 2 3 4 × 5 6 7 8 ⍝ 5 12 21 32
|
|
|
|
|
|
|
|
|
|
|
|
⍝ All functions have single-argument and dual-argument
|
|
|
|
|
|
⍝ meanings. For example, "×" applied to two arguments
|
2024-05-12 10:38:39 +00:00
|
|
|
|
⍝ means multiply, but when applied to only a right-hand
|
2024-05-12 10:34:52 +00:00
|
|
|
|
⍝ side, it returns the sign:
|
|
|
|
|
|
|
|
|
|
|
|
× ¯4 ¯2 0 2 4 ⍝ ¯1 ¯1 0 1 1
|
|
|
|
|
|
|
|
|
|
|
|
⍝ Values can be compared using these operators (1 means
|
|
|
|
|
|
⍝ "true", 0 means "false"):
|
|
|
|
|
|
|
|
|
|
|
|
10 20 30 = 10 20 99 ⍝ 1 1 0
|
|
|
|
|
|
|
|
|
|
|
|
10 20 30 < 10 20 99 ⍝ 0 0 1
|
|
|
|
|
|
|
|
|
|
|
|
⍝ "⍳n" returns a vector containing the first n naturals.
|
|
|
|
|
|
⍝ Matrices can be constructed using ⍴ (reshape):
|
|
|
|
|
|
4 3 ⍴ ⍳5 ⍝ 0 1 2
|
|
|
|
|
|
⍝ 3 4 0
|
|
|
|
|
|
⍝ 1 2 3
|
|
|
|
|
|
⍝ 4 0 1
|
|
|
|
|
|
|
|
|
|
|
|
⍝ Single-argument ⍴ gives you the dimensions back:
|
|
|
|
|
|
⍴ 4 3 ⍴ ⍳5 ⍝ 4 3
|
|
|
|
|
|
|
|
|
|
|
|
⍝ Values can be stored using ←. Let's calculate the mean
|
|
|
|
|
|
⍝ value of a vector of numbers:
|
|
|
|
|
|
A ← 10 60 55 23
|
|
|
|
|
|
|
|
|
|
|
|
⍝ Sum of elements of A (/ is reduce):
|
|
|
|
|
|
+/A ⍝ 148
|
|
|
|
|
|
|
|
|
|
|
|
⍝ Length of A:
|
|
|
|
|
|
⍴A ⍝ 4
|
|
|
|
|
|
|
|
|
|
|
|
⍝ Mean:
|
|
|
|
|
|
(+/A) ÷ (⍴A) ⍝ 37
|
|
|
|
|
|
|
|
|
|
|
|
⍝ We can define this as a function using {} and ⍵:
|
|
|
|
|
|
mean ← {(+/⍵)÷⍴⍵}
|
|
|
|
|
|
mean A ⍝ 37
|
2024-05-12 10:38:39 +00:00
|
|
|
|
```
|
