Contents

Published in HTML by Kx Systems, by permission. Please notify any errors in this edition to [email protected].

Q for Mortals   An introduction to q programming
by Jeffry A. Borror, q4m LLC
Version 3.1

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• Preface
• 0. Overview
  • 0.0 The Evolution of Q
  • 0.1 Philosophy
  • 0.2 Mathematics Refresher
• 1. Q Shock and Awe
  • 1.1 Starting q
  • 1.2 Variables
  • 1.3 Whitespace
  • 1.4 The Q Console
  • 1.5 Comments
  • 1.6 Assignment
  • 1.7 Order of Evaluation
  • 1.8 Data Types 101
  • 1.9 Lists 101
  • 1.10 Functions 101
  • 1.11 Functions on Lists 101
  • 1.12 Example: Fibonacci Numbers
  • 1.13 Example: Newton’s Method for n^th Roots
  • 1.14 Example: FIFO Allocation
  • 1.15 Dictionaries and Tables 101
  • 1.16 q-sql 101
  • 1.17 Example: Trades Table
  • 1.18 File I/O 101
  • 1.19 Interprocess Communication101
  • 1.20 Example: Asynchronous Callbacks
  • 1.21 Websockets 101
• 2. Basic Data Types: Atoms
  • 2.0 Overview
  • 2.1 Integer Data
  • 2.2 Floating Point Data
  • 2.3 Binary Data
  • 2.4 Text Data
  • 2.5 Temporal Data
  • 2.6 Arithmetic Infinities and Nulls
  • 2.7 Nulls
• 3. Lists
  • 3.0 Overview
  • 3.1 Introduction to Lists
  • 3.2 Simple Lists
  • 3.3 Empty and Singleton Lists
  • 3.4 Indexing
  • 3.5 Combining Lists
  • 3.6 Lists as Maps
  • 3.7 Nesting
  • 3.8 Iterated Indexing and Indexing at Depth
  • 3.9 Indexing with Lists
  • 3.10 Elided Indices
  • 3.11 Rectangular Lists and Matrices
  • 3.12 Useful List Operations
• 4. Operators
  • 4.0 Operators and Keywords Are Functions
  • 4.1 Operator Precedence
  • 4.2 Match (~)
  • 4.3 Equality and Relational Operators
  • 4.4 Basic Arithmetic: +, -, *, %
  • 4.5 Greater (|) and Lesser (&)
  • 4.6 Amend (:)
  • 4.7 Exponential Primitives: sqrt, exp, log, xexp, xlog
  • 4.8 More Numeric Primitives
  • 4.9 Operations on Temporal Values
  • 4.10 Operations on Infinities and Nulls
  • 4.11 Alias (::)
• 5. Dictionaries
  • 5.0 Overview
  • 5.1 Dictionary Basics
  • 5.2 Operations on Dictionaries
  • 5.3 Column Dictionaries
  • 5.4 Flipping a Column Dictionary
• 6. Functions
  • 6.0 Overview
  • 6.1 Function Specification
  • 6.2 Call-by-Name
  • 6.3 Local and Global Variables
  • 6.4 Projection
  • 6.5 Everything Is a Map
  • 6.6 Atomic Functions
  • 6.7 Iterators
  • 6.8 General Application
• 7. Transforming Data
  • 7.1 Types
  • 7.2 Cast
  • 7.3 Data to and from Text
  • 7.4 Creating Typed Empty Lists
  • 7.5 Enumerations
• 8. Tables
  • 8.0 Overview
  • 8.1 Table Definition
  • 8.2 Empty Tables and Schema
  • 8.3 Basic select and update
  • 8.4 Primary Keys and Keyed Tables
  • 8.5 Foreign Keys and Virtual Columns
  • 8.6 Working with Tables and Keyed Tables
  • 8.7 Complex Column Data
  • 8.8 Attributes
• 9. Queries: q-sql
  • 9.0 Overview
  • 9.1 Inserting Records
  • 9.2 upsert
  • 9.3 The select Template
  • 9.5 The update Template
  • 9.6 The delete Template
  • 9.7 Sorting
  • 9.8 Renaming and Rearranging Columns
  • 9.9 Joins
  • 9.10 Parameterized Queries
  • 9.11 Views
  • 9.12 Functional Forms
  • 9.13 Examples
• 10. Execution Control
  • 10.0 Overview
  • 10.1 Control Flow
  • 10.2 Debugging
  • 10.3 Scripts
• 11. I/O
  • 11.0 Overview
  • 11.1 Binary Data
  • 11.2 Save and Load on Tables
  • 11.3 Splayed Tables
  • 11.4 Text Data
  • 11.5 Parsing Records
  • 11.6 Interprocess Communication
  • 11.7 HTTP and Web sockets
• 12. Workspace Organization
  • 12.0 Overview
  • 12.1 Namespaces
  • 12.2 Contexts
  • 12.3 Creating Contexts
  • 12.4 Context as Dictionary
  • 12.5 Expunging from a Context
  • 12.6 Saving and Loading Contexts
  • 12.7 Working in a Context
• 13. Commands and System Variables
  • 13.1 Command Format
  • 13.2 Command Line Parameters
  • 13.3 System Variables
• 14. Introduction to Kdb+
  • 14.0 Overview
  • 14.1 Tables in Memory and Serialization
  • 14.2 Splayed Tables
  • 14.3 Partitioned Tables
  • 14.4 Segmented Tables
  • 14.5 Utilities for Splaying and Partitioning
  • 14.6 Kdb Database
  • 14.7 Putting It All Together
  • 14.8 There's No Place Like QHOME
• Appendix A. Built-in Functions
  • A.0 Overview
  • A.1 acos
  • A.2 all
  • A.3 and
  • A.4 any
  • A.5 asc
  • A.6 asin
  • A.7 atan
  • A.8 attr
  • A.9 avg
  • A.10 avgs
  • A.11 bin
  • A.12 binr
  • A.13 Roll/Deal (?)
  • A.14 Enum Extend (?)
  • A.15 cor
  • A.16 count
  • A.17 cov
  • A.18 cross
  • A.19 cut
  • A.20 Cut (_)
  • A.21 deltas
  • A.22 desc
  • A.23 dev
  • A.24 differ
  • A.25 distinct
  • A.26 enlist
  • A.27 eval
  • A.28 except
  • A.29 exit
  • A.30 Fill (^)
  • A.31 Find (?)
  • A.32 fills
  • A.33 flip
  • A.34 getenv
  • A.35 group
  • A.36 gtime
  • A.37 iasc
  • A.38 identity
  • A.39 idesc
  • A.40 in
  • A.41 inter
  • A.42 inv
  • A.43 Join (,)
  • A.44 key
  • A.45 like
  • A.46 lower
  • A.47 lsq
  • A.48 ltime
  • A.49 ltrim
  • A.50 mavg
  • A.51 max
  • A.52 maxs
  • A.53 mcount
  • A.54 md5
  • A.55 mdev
  • A.56 med
  • A.57 min
  • A.58 mins
  • A.59 mmax
  • A.60 mmin
  • A.61 mmu
  • A.62 msum
  • A.63 next
  • A.64 null
  • A.65 or
  • A.66 over
  • A.67 parse
  • A.68 peach
  • A.68.1 Threads
  • A.68.2 Distributed peach
  • A.69 prd
  • A.70 prds
  • A.71 prev
  • A.72 prior
  • A.73 rank
  • A.74 ratios
  • A.75 raze
  • A.76 reval
  • A.77 reverse
  • A.78 rload
  • A.79 rotate
  • A.80 rsave
  • A.81 rtrim
  • A.82 scan
  • A.83 scov
  • A.84 sdev
  • A.85 setenv
  • A.86 sin
  • A.87 ss
  • A.88 ssr
  • A.89 string
  • A.90 sublist
  • A.91 sum
  • A.92 sums
  • A.93 sv
  • A.94 svar
  • A.95 system
  • A.96 Take/Reshape (#)
  • A.97 tan
  • A.98 til
  • A.99 trim
  • A.100 ungroup
  • A.101 union
  • A.102 upper
  • A.103 value
  • A.104 var
  • A.105 vs
  • A.106 wavg
  • A.107 where
  • A.108 within
  • A.109 wsum
  • A.110 xbar
  • A.111 xprev
  • A.112 xrank
• Appendix B. Error Messages
  • B.1 Runtime Errors
  • B.2 Parse Errors
  • B.3 System Errors