Representation-dependent gene-level operations  
        for genetic and evolutionary algorithms with real-coded genes
        used in the R-package 'xega' <https://CRAN.R-project.org/package=xega>
        are collected in this package. The common feature of the gene
        operations is that all of them are useful for derivation-free
        optimization algorithms. At the moment the package  
        implements initialization, mutation, crossover, and replication 
        operations for differential evolution as described in
        Price, Kenneth V., Storn, Rainer M. and Lampinen, Jouni A. (2005)
        <doi:10.1007/3-540-31306-0>.  In addition, several (more recent) 
        methods for determining the scale factor are provided.
        For 'xega''s architecture,
        see Geyer-Schulz, A. (2025) <doi:10.5445/IR/1000187255>.

Representation-dependent gene level operations of a 
        genetic algorithm with binary coded genes
        for the R-package 'xega' <https://CRAN.R-project.org/package=xega>:
        Initialization of random binary genes, several gene maps for 
        binary genes, several mutation operators, several crossover
        operators with 1 and 2 kids, replication 
        pipelines for 1 and 2 kids, and, last but not least, function 
        factories for configuration. 
        See Goldberg, D. E. (1989, ISBN:0-201-15767-5).
        For crossover operators, see 
        Syswerda, G. (1989, ISBN:1-55860-066-3),
        Spears, W. and De Jong, K. (1991, ISBN:1-55860-208-9).
        For mutation operators, see 
        Stanhope, S. A. and Daida, J. M. (1996, ISBN:0-18-201-031-7).
        For 'xega''s architecture,
        see Geyer-Schulz, A. (2025) <doi:10.5445/IR/1000187255>.

Grammatical evolution  (see O'Neil, M. and 
        Ryan, C.  (2003,ISBN:1-4020-7444-1)) uses decoders to 
        convert linear (binary or integer genes) into programs.  
        In addition, automatic determination of codon precision 
        with a limited rule choice bias is provided.
        For a recent survey of grammatical evolution, 
        see Ryan, C., O'Neill, M., and Collins, J. J. (2018)
        <doi:10.1007/978-3-319-78717-6>.