GrammarRandomExpression: Random Expression Generation

In fnoorian/gramEvol: Grammatical Evolution for R

Random Expression Generation

Description

Creates random expressions from context-free grammar.

Usage

GrammarRandomExpression(grammar, 
          numExpr = 1, 
          max.depth = length(grammar$def), 
          startSymb = GrammarStartSymbol(grammar),
          max.string = GrammarMaxSequenceRange(grammar, max.depth, startSymb, 
                                               approximate = TRUE), 
          wrappings = 3, 
          retries = 100)

Arguments

grammar	A grammar object.
numExpr	Number of random expressions to generate.
max.depth	Maximum depth of recursion, in case of a cyclic grammar. By default it is limited to the number of production rules in the grammar.
startSymb	The symbol where the generation of a new expression should start.
max.string	Maximum value for each element of the sequence.
wrappings	The number of times the function is allowed to wrap around inputString if non-terminal symbols are still remaining.
retries	Number of retries until a terminal and valid expressions is found.

Details

GrammarRandomExpression creates num.expr random expressions from the given grammar. It can be used to quickly examine the expressibility of the grammar, or as a form of random search over the grammar.

Value

An expressions, or a list of expressions.

Examples

# Define a simple grammar
# <expr> ::= <var><op><var>
# <op>   ::= + | - | *
# <var>  ::= A | B | C
ruleDef <- list(expr = gsrule("<var><op><var>"),
                op =   gsrule("+", "-", "*"),
                var =  grule(A, B, C))

# Create a grammar object
grammarDef <- CreateGrammar(ruleDef)

# Generate 5 random expressions
exprs <- GrammarRandomExpression(grammarDef, 5)
print(exprs)

fnoorian/gramEvol documentation built on July 5, 2023, 6:38 p.m.