expression.info.ipynb

Kernel: Python 3

expression.info(key=None)

A dictionary of facts about an expression.

The keys of the dictionary are:

• length, size: the number of nodes in the syntax tree

• width, atom: the number of letter occurrences

• depth: the depth of the syntax tree (the depth of $a$ is 0, not 1)

• type: the implementation type

• add, complement, etc.: the number of occurrences of these operators (+, {c}, etc.) in the expression

Arguments:

• key: if specified, return just the corresponding result.

See also:

• expression.context

Examples

import vcsn
e = vcsn.Q.expression('[ab]*a[ab]')
e

$\left(a + b\right)^{*} \, a \, \left(a + b\right)$

e.SVG()

e.info()

{'add': 2,
 'atom': 5,
 'complement': 0,
 'compose': 0,
 'conjunction': 0,
 'depth': 3,
 'infiltrate': 0,
 'ldivide': 0,
 'length': 10,
 'lweight': 0,
 'mul': 1,
 'one': 0,
 'rweight': 0,
 'shuffle': 0,
 'size': 10,
 'star': 1,
 'transposition': 0,
 'tuple': 0,
 'type': 'expressionset<letterset<char_letters(ab)>, q>',
 'width': 5,
 'zero': 0}

e.info('type')

'expressionset<letterset<char_letters(ab)>, q>'

Note that, although the expression uses a variadic product (the . node features three children), the length corresponds to the usual definition of expressions based on binary node. Hence the tree features 9 nodes, but the length of the expression is 10. This applies to all the variadic operators.

e.info('length')

10

e.info('depth')

3

e = vcsn.Q.expression('[ab]*a[ab]{2} & [ab]*a[ab]{4}')
e

$\left(a + b\right)^{*} \, a \, \left(a + b\right)^{2} \& \left(a + b\right)^{*} \, a \, \left(a + b\right)^{4}$

e.SVG()

e.info()

{'add': 8,
 'atom': 18,
 'complement': 0,
 'compose': 0,
 'conjunction': 1,
 'depth': 4,
 'infiltrate': 0,
 'ldivide': 0,
 'length': 37,
 'lweight': 0,
 'mul': 2,
 'one': 0,
 'rweight': 0,
 'shuffle': 0,
 'size': 37,
 'star': 2,
 'transposition': 0,
 'tuple': 0,
 'type': 'expressionset<letterset<char_letters(ab)>, q>',
 'width': 18,
 'zero': 0}

vcsn.Q.expression('[ab]a[ab]').info()

{'add': 2,
 'atom': 5,
 'complement': 0,
 'compose': 0,
 'conjunction': 0,
 'depth': 2,
 'infiltrate': 0,
 'ldivide': 0,
 'length': 9,
 'lweight': 0,
 'mul': 1,
 'one': 0,
 'rweight': 0,
 'shuffle': 0,
 'size': 9,
 'star': 0,
 'transposition': 0,
 'tuple': 0,
 'type': 'expressionset<letterset<char_letters(ab)>, q>',
 'width': 5,
 'zero': 0}