Verbs Classification - kevinlawler/kona GitHub Wiki

Verbs (semantic table)

Verbs in K — that's what operations in imperative languages are. When you add two numbers in Python, you use an operation "+" (plus).

Python 3.2 (r32:88445, Apr 15 2011, 11:09:05) 
[GCC 4.5.2 20110127 (prerelease)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> 12 + 23
35

Verbs in K serve the same purpose.

K Console - Enter \ for help
  12 + 23
35

Yeah, it's too simple, I agree 😄 . But wait! While verbs are similar to operators, they have some distinctions:

• verbs in K have one-symbol length! Here is the full list: ~!@#$%^&*-_=+|.<>. Every symbol has its own meaning. The one difficulty is to remember all purposes…
• verbs can be used in two modes — prefix and infix. Prefix usage is called "monadic", infix — "dyadic". One verb can have different meanings in monadic and dyadic usages.
• though syntax seems complicated, semantic is rudimentary when you know the classification. Almost all verbs can be divided into 4 groups by method of data modification:
  • Generative verbs — they create data
  • Modifying verbs — they make changes to data and do not change data length
  • Transforming verbs — they modify data, change shape, replace with other data
  • Reflection verbs — take a look on data, examine shape, result of operation is only one data item

Almost all the features and all K verbs have analogues in other languages, but only in APL-based they have 1-char-long syntax. This saves time for "parse-interpret" process.

Generation — creates new enumerations

• ! monadic — enumerate
• # dyadic n#m — fill

Modification — make modification of enumeration, do not change length

• + dyadic — add
• * dyadic — multiply
• % monadic, dyadic — divide
• - monadic, dyadic — subtract
• | monadic, dyadic — reverse, MAX/or
• & diadic — AND/min
• ^ diadic — power
• ~ monadic — not
• ! dyadic — mod/rotate
• < dyadic — less
• > dyadic — greater
• = dyadic — equal
• _ monadic — floor

Transform — make modification of enumeration, may change length, shape, meaning

• + monadic — transpose
• & monadic — where
• = monadic — group
• < monadic — grade up
• > monadic — grade down
• ? monadic — unique
• , dyadic — join
• _ dyadic — cut lower/reshape
• # dyadic n#y — fill by list
• # dyadic n#y, length of y > n — cut upper

Meta — returns one item or information on enumeration

• * monadic — take first
• # monadic — count
• ^ monadic — shape
• ~ dyadic — full equal
• @ monadic, dyadic — atom/at
• , monadic — create one item list
• . dyadic — value at
• ? dyadic x?n version — find