regex101: PCRE (Legacy) Match Workspace

Explanation

Pro

Group rulename(?P<rulename><\S+>)

<the literal < (60₁₀ / 74₈ / 3C₁₆)

\S+any non-whitespace character, repeated at least once

>the literal > (62₁₀ / 76₈ / 3E₁₆)

\s*any whitespace character, repeated any number of times

::=the literal text ::=

\s*any whitespace character, repeated any number of times

Group production(?P<production>(?:(?=\#)\#[^\r\n]*|(?!<\S+>\s*::=).+?)+)

Non-Capturing Group(?:(?=\#)\#[^\r\n]*|(?!<\S+>\s*::=).+?)+

+repeats the group contents below at least once:

1st Alternative(?=\#)\#[^\r\n]*

Positive Lookahead(?=\#)

\#the literal # (35₁₀ / 43₈ / 23₁₆)

Negated Character Class[^\r\n]*

*matches any number of characters outside the set below:

\ra carriage return (ASCII 13)

\na line-feed (newline) character (ASCII 10)

2nd Alternative(?!<\S+>\s*::=).+?

Negative Lookahead(?!<\S+>\s*::=)

<the literal < (60₁₀ / 74₈ / 3C₁₆)

\S+any non-whitespace character, repeated at least once

>the literal > (62₁₀ / 76₈ / 3E₁₆)

\s*any whitespace character, repeated any number of times

::=the literal text ::=

.+?any character, repeated at least once

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

s modifier: single line. Allows a dot to match line terminators

Quick Reference

25 tokens

Regular Expression

(?P<rulename><\S+>)\s*::=\s*(?P<production>(?:(?=\#)\#[^\r\n]*|(?!<\S+>\s*::=).+?)+)

New

# *****************************************************************************
# Smallest grammar
# *****************************************************************************

# structure

<predefined> ::= 'b0 = b1 = b2 = bool()'
                 'i0 = i1 = i2 = int()'
                 'res = int()'
                 <code>

# *****************************************************************************
<bool_var> ::= 'b0' | 'b1' | 'b2'
<int_var> ::= 'i0' | 'i1' | 'i2' | 'in0' | 'in1' | 'in2' | 'in3' | 'res'
# *****************************************************************************

<code> ::= <code><code> | <statement>'\n'

<statement> ::= <assign> | <compound_stmt>
<compound_stmt> ::= <if> | <while>

            # from bool
<assign> ::= <bool_assign>
           # from int
           | <int_assign>

<if> ::= <if-then> | <if-then><else>

<if-then> ::= 'if '<bool><block>
<else> ::= 'else'<block>

<block> ::= ':{:\n'<code>':}'


<while> ::= <loop-header>'while '<bool><loop-block>