RosettaCodeData/Task/Extend-your-language/PARI-GP/extend-your-language-3.pari

install("if2","GGDEDEDEDE","if2","./if2.gp.so");
addhelp(if2, "if2(a,b,{seq1},{seq2},{seq3},{seq4}): if a is nonzero and b is nonzero, seq1 is evaluated; if a is nonzero and b is zero, seq2 is evaluated; if a is zero and b is nonzero, seq3 is evaluated; otherwise seq4. seq1 through seq4 are optional.");