makeRule {xegaBNF}

Transforms a single BNF rule into a production table.

Description

makeRule() transforms a single BNF rule into a production table.

Usage

makeRule(Rule, ST)

Arguments

Rule

A rule.

ST

A symbol table.

Details

Because a single BNF rule can provide a set of substitutions, more than one line in a production table may result. The number of substitutions corresponds to the number of lines in the production table.

Value

A named list with 2 elements, namely $LHS and $RHS. The left-hand side $LHS is a vector of non-terminal identifiers and the right-hand side $RHS is a vector of vectors of numerical identifiers. The list represents the substitution of $LHS[i] by the identifier list $RHS[[i]].

Examples

c<-booleanGrammar()$BNF
ST<-makeSymbolTable(c)
c<-booleanGrammar()$BNF 
b<-strsplit(c,";")[[1]]
a<-b[2:4]
a<-gsub(pattern=";",replacement="", paste(a[1], a[2], a[3], sep=""))
makeRule(a, ST)