Operators

Arithmetic

Operator	Meaning	Example	Result
+	Addition	10 + 3	13
-	Subtraction	10 - 3	7
*	Multiplication	10 * 3	30
/	Float division	10 / 3	3.333...
//	Integer division	10 // 3	3
%	Modulo	10 % 3	1
**	Exponentiation	2 ** 8	256

/ always returns a Float. Use // (borrowed from Fortran) when you want a whole-number result.

puts 10 / 3    # 3.3333333333333335
puts 10 // 3   # 3
puts 10 % 3    # 1
puts 2 ** 10   # 1024

* and ** also work on strings and vectors:

puts "ha" * 3        # hahaha
puts [0] * 4         # [0, 0, 0, 0]
puts [1, 2] * 3      # [1, 2, 1, 2, 1, 2]

---

Compound Assignment

Shorthand for x = x op value:

x = 10
x += 3    # 13
x -= 2    # 11
x *= 4    # 44
x /= 2    # 22.0  (float division)
x //= 5   # 4     (integer division)
x **= 2   # 16
x %= 5    # 1

Works on vector elements too:

v = [10, 20, 30]
v[0] += 5
puts v   # [15, 20, 30]

---

Comparison

Comparison operators return true or false.

Operator	Meaning
==	Equal
!=	Not equal
<	Less than
<=	Less than or equal
>	Greater than
>=	Greater than or equal

puts 5 == 5     # true
puts 5 != 3     # true
puts 5 > 3      # true
puts 5 < 3      # false
puts 5 >= 5     # true
puts 5 <= 4     # false

# Integers and Floats compare naturally
puts 3 == 3.0   # true
puts 3 < 3.14   # true

# Strings compare lexicographically
puts "apple" < "banana"   # true
puts "z" > "a"            # true

---

Logical

Operator	Meaning	Example
and	Both must be true	x > 0 and x < 10
or	At least one must be true	x < 0 or x > 100
not	Negate	not active

age    = 25
active = true

if age >= 18 and active
  puts "eligible"
end

if age < 0 or age > 120
  puts "invalid age"
end

if not active
  puts "inactive"
end

Short-circuit evaluation applies — and stops at the first false, or stops at the first true.

---

Match Operator =~

Returns the position of the first regex match, or nil if there is no match.

puts "frank123" =~ "\\d+"    # 5
puts "no digits" =~ "\\d+"   # nil

pos = "hello world" =~ "world"
if pos != nil
  puts "found at position #{pos}"   # found at position 6
end

---

String Concatenation +

puts "Hello, " + "Frankie!"   # Hello, Frankie!

first = "Frank"
last  = "ie"
puts first + last              # Frankie

---

Hash Merge |

Merges two hashes. Right-hand keys win on conflict.

defaults = {color: "blue", size: "md", weight: "normal"}
custom   = {color: "red", size: "lg"}

result = defaults | custom
puts result   # {color: red, size: lg, weight: normal}

# Chains naturally
base = {a: 1, b: 2}
mid  = {b: 3, c: 4}
top  = {c: 5, d: 6}
puts base | mid | top   # {a: 1, b: 3, c: 5, d: 6}

---

Pipe Operator |>

Passes the result of the left side as the argument to the right side. Borrowed from R.

[1, 2, 3, 4, 5] |> sum             # 15
[1, 2, 3, 4, 5] |> mean            # 3.0
[1, 2, 3, 4, 5] |> sum |> puts     # 15

def double(x)
  x * 2
end

10 |> double |> puts   # 20

# Clean data pipelines
data = [3, 1, 4, 1, 5, 9, 2, 6, 5, 3]
data |> sum |> puts    # 39
data |> mean |> puts   # 3.9
data |> stdev |> puts  # 2.375...

---

Nil-Safe Navigation &.

Calls a method only if the receiver is not nil. Returns nil otherwise — no crash.

name = nil
puts name&.upcase         # nil
puts name&.upcase&.length # nil — chain short-circuits

user = {name: "Alice"}
puts user["name"]&.upcase          # ALICE
puts user["missing_key"]&.upcase   # nil

---

Range Operators

Operator	Meaning	Example
..	Inclusive range	1..5 → 1, 2, 3, 4, 5
...	Exclusive range	1...5 → 1, 2, 3, 4

Used in loops, slices, and vec():

for i in 1..5
  puts i
end

puts "hello"[1..3]    # ell
puts vec(1..10)       # [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
puts vec(0...5)       # [0, 1, 2, 3, 4]

---

Operator Precedence

From highest to lowest:

Level	Operators
Highest	**
	* / // %
	+ -
	< <= > >=
	== != =~
	and
	or
	\|>
Lowest	\| (hash merge)

Use parentheses to make intent explicit:

puts 2 + 3 * 4      # 14  — * before +
puts (2 + 3) * 4    # 20  — parentheses first