compileShortPT {xegaBNF}

Produces a production table with non-recursive productions only.

Description

compileShortPT() produces a “short” production table from a context-free grammar. The short production table does not contain recursive production rules. Warning: No error checking implemented.

Usage

compileShortPT(G)

Arguments

G

A grammar with symbol table ST, production table PT, and start symbol Start.

Details

compileShortPT() starts with production rules whose right-hand side contains only terminals. It incrementally builds up the new PT until at least one production rule sequence from a non-terminal to a terminal symbol.

The short production rule provides for each non-terminal symbol a minimal finite derivation into terminals. Instead of the full production table, it is used for generating depth-bounded derivation trees.

Value

A (short) production table is a named list with 2 columns. The first column (the left-hand side LHS) is a vector of non-terminal identifiers. The second column (the right-hand side RHS) is a vector of vectors of numerical identifiers. LHS[i] derives into RHS[i].

Examples

g<-compileBNF(booleanGrammar())
compileShortPT(g)