Variables

There are four kinds of variables in Pip:

• Local variables have different bindings at each scope level. Only their values at the current scope are accessible.
• Global variables have the same bindings anywhere in a Pip program. Many of them have useful initial values.
• Special variables have side effects when accessed and/or assigned.
• Regex match variables can be accessed normally, but they are automatically set each time a regex match is completed. See also the section on regex in Pip.

Note: unlike other lowercase letters, j is not a variable; it is reserved for future use.

Local variables

a First argument of the current function (at top level, first argument to the main program)

b Second argument of the current function (at top level, second argument to the main program)

c Third argument of the current function (at top level, third argument to the main program)

d Fourth argument of the current function (at top level, fourth argument to the main program)

e Fifth argument of the current function (at top level, fifth argument to the main program)

f The current function (at top level, the main program as a function)

g Full list of arguments of the current function (at top level, full list of arguments to the main program)

Global variables

Note: any sequence of two uppercase letters that isn’t a command or an operator is a global variable. The ones not listed here are initialized to nil.

_ Identity function (== {a})

h 100

i 0

k ", "

l Empty list

m 1000 (mnemonic: Roman numeral M)

n Newline character

o 1

p "()"

s Space character

t 10

u Nil

v -1

w Pattern matching one or more whitespace characters (\`\s+\`)

x Empty string

y Empty string (modified by Y operator)

z Lowercase alphabet a to z

B Block that returns its second argument ({b})

G Block that returns its argument list ({g})

\a First argument to the main program

\b Second argument to the main program

\c Third argument to the main program

\d Fourth argument to the main program

\e Fifth argument to the main program

\f The main program as a function

\g Full list of arguments to the main program

AZ Uppercase alphabet A to Z

CZ Lowercase consonants b to z

PA All Printable ASCII characters, 32 through 126

PI Pi (3.141592653589793)

VD Date of the latest interpreter update in YYYY-MM-DD format

VN Current version number in X.Y.Z format

VW Lowercase vowels a to u

VY Lowercase vowels a to y

XA Pattern matching one (ASCII) letter (\`[A-Za-z]\`)

XC Pattern matching one (lowercase ASCII) consonant (\`[bcdfghjklmnpqrstvwxyz]\`)

XD Pattern matching one digit (\`\d\`)

XI Pattern matching an integer (\`-?\d+\`)

XL Pattern matching one lowercase (ASCII) letter (\`[a-z]\`)

XN Pattern matching an integer or decimal number (\`-?\d+(?:\.\d+)?\`)

XU Pattern matching one uppercase (ASCII) letter (\`[A-Z]\`)

XV Pattern matching one (lowercase ASCII) vowel, not including y (\`[aeiou]\`)

XW Pattern matching one word character–letter, number, or underscore (\`\w\`)

XX Pattern matching any one character (\`.\`)

XY Pattern matching one (lowercase ASCII) vowel, including y (\`[aeiouy]\`)

Special variables

q Reads and returns a line of input each time it is accessed

r Returns a random number 0 <= r < 1 when it is accessed; assigning to r seeds the random-number generator

Regex match variables

$0 Entire match

$1 Contents of capture group 1 (and similarly for 2-9)

$$ List of all capture group contents

$( Start index of match

$) End index of match

$[ List of start indices of capture groups

$] List of end indices of capture groups

$` The part of the string before the match

$' The part of the string after the match