First

First is an esolang invented by User:None1. It's the author's first esolang invented on the first day of 2026, thus the name. It's also the first esolang with a full specification invented in 2026.

Memory

There's an integer set. Integers are unbounded.

Commands

x and y are integer literals.

• F x: Flip the existence of x in the set (i.e.: Delete x if it exists, otherwise insert x}}).
• I x: Insert x.
• R: Read integer from input (either as character or number) and insert.
• S: Search for the smallest element in the set and output (either as character or number). If such element doesn't exist (i.e.: the set is empty), the program terminates.
• T x y: Transfer to label x if y exists in the set.
• x: Label.

Commands are case insensitive.

Examples

Hello, world!

I 72
S
F 72
F 101
S
F 101
F 108
S
F 108
F 108
S
F 108
F 111
S
F 111
F 44
S
F 44
F 32
S
F 32
F 119
S
F 119
F 111
S
F 111
F 114
S
F 114
F 108
S
F 108
F 100
S
F 100
F 33
S

Truth machine

R
2026
S
T 2026 1

Cat (never terminates)

I 1000000000
2026
R
S
T 2026 1000000000

Doesn't work for integers over 1000000000.