program::keyword_t program::_keywords[] =
{
    //GENERAL
    { cmd_keyword, "", NULL, "\nGENERAL"},
    { cmd_keyword, "nop", &program::nop, "no operation"},
    { cmd_keyword, "?", &program::help, "" },
    { cmd_keyword, "h", &program::help, "" },
    { cmd_keyword, "help", &program::help, "(or h or ?) this help message" },
    { cmd_keyword, "q", &program::good_bye, "" },
    { cmd_keyword, "quit", &program::good_bye, "(or q or exit) quit software" },
    { cmd_keyword, "exit", &program::good_bye, "" },
    { cmd_keyword, "verbose", &program::verbose, "set verbosity, from 0 (not verbose) to > 0" },
    { cmd_keyword, "test", &program::test, "" }, //not seen by user

	//ALGEBRA
	{ cmd_undef, "", NULL, "\nALGEBRA"},
	{ cmd_keyword, "+", &program::plus, "binary operator +" },
	{ cmd_keyword, "-", &program::minus, "binary operator -" },
	{ cmd_keyword, "neg", &program::neg , "unary operator - (negation)" },
	{ cmd_keyword, "*", &program::mul, "binary operator *" },
	{ cmd_keyword, "/", &program::div, "binary operator /" },

	//TEST
	{ cmd_undef, "", NULL, "\nTEST"},
	{ cmd_keyword, ">", &program::sup, "binary operator >" },
	{ cmd_keyword, ">=", &program::sup_eq, "binary operator >=" },
	{ cmd_keyword, "<", &program::inf, "binary operator <" },
	{ cmd_keyword, "<=", &program::inf_eq, "binary operator <=" },
	{ cmd_keyword, "!=", &program::diff, "binary operator != (different)" },
	{ cmd_keyword, "==", &program::eq , "binary operator == (equal)" },

	//STACK
	{ cmd_undef, "", NULL, "\nSTACK"},
	{ cmd_keyword, "swap", &program::swap, "swap 2 first stack entries" },
	{ cmd_keyword, "drop", &program::drop, "drop first stack entry" },
	{ cmd_keyword, "drop2", &program::drop2, "drop 2 first stack entries" },
	{ cmd_keyword, "erase", &program::erase, "drop all stack entries" },
	{ cmd_keyword, "rot", &program::rot, "rotate 3 first stack entries" },
	{ cmd_keyword, "dup", &program::dup, "duplicate first stack entry" },
	{ cmd_keyword, "dup2", &program::dup2, "duplicate 2 first stack entries" },
	{ cmd_keyword, "pick", &program::pick, "push a copy of  the given stack level onto the stack" },
	{ cmd_keyword, "depth", &program::depth, "give stack depth" },

	//BRANCH
	{ cmd_undef, "", NULL, "\nBRANCH"},
	{ cmd_branch, "if", (program_fn_t)&program::rpn_if, "<test-instructions>" },
	{ cmd_branch, "then", (program_fn_t)&program::rpn_then, "<true-instructions>" },
	{ cmd_branch, "else", (program_fn_t)&program::rpn_else, "<false-instructions>" },
	{ cmd_keyword, "end", &program::rpn_end, "(end of if structure)" },
	{ cmd_branch, "start", (program_fn_t)&program::rpn_start, "repeat instructions several times" },
	{ cmd_branch, "for", (program_fn_t)&program::rpn_for, "repeat instructions several times with variable" },
	{ cmd_branch, "next", (program_fn_t)&program::rpn_next, "ex: 1 10 start <instructions> next" },
	{ cmd_branch, "step", (program_fn_t)&program::rpn_step, "ex: 1 100 start <instructions> 4 step" },

	//STORE
	{ cmd_undef, "", NULL, "\nSTORE"},
	{ cmd_keyword, "sto", &program::sto, "store a variable. ex: 1 'name' sto" },
	{ cmd_keyword, "rcl", &program::rcl, "recall a variable. ex: 'name' rcl" },
	{ cmd_keyword, "purge", &program::purge, "delete a variable. ex: 'name' purge" },
	{ cmd_keyword, "vars", &program::vars, "list all variables" },

	//TRIG
	{ cmd_undef, "", NULL, "\nTRIG"},
	{ cmd_keyword, "pi", &program::pi, "PI constant" },
	{ cmd_keyword, "sin", &program::rpn_sin, "sinus" },
	{ cmd_keyword, "asin", &program::rpn_asin, "arg sinus" },
	{ cmd_keyword, "cos", &program::rpn_cos , "cosinus" },
	{ cmd_keyword, "acos", &program::rpn_acos, "arg cosinus" },
	{ cmd_keyword, "tan", &program::rpn_tan, "tangent" },
	{ cmd_keyword, "atan", &program::rpn_atan, "arg tangent" },
	{ cmd_keyword, "d->r", &program::d2r, "convert degrees to radians" },
	{ cmd_keyword, "r->d", &program::r2d, "convert radians to degrees" },    

	//LOGS
	{ cmd_undef, "", NULL, "\nLOGS"},
	{ cmd_keyword, "e", &program::rpn_e, "exp(0) constant" },
	{ cmd_keyword, "log", &program::rpn_log, "logarithm base 10" },
	{ cmd_keyword, "alog", &program::rpn_alog, "exponential base 10" },
	{ cmd_keyword, "ln", &program::rpn_ln, "logarithm base e" },
	{ cmd_keyword, "exp", &program::rpn_exp, "exponential" },
	{ cmd_keyword, "sinh", &program::rpn_sinh, "hyperbolic sine" },
	{ cmd_keyword, "asinh", &program::rpn_asinh, "inverse hyperbolic sine" },
	{ cmd_keyword, "cosh", &program::rpn_sinh, "hyperbolic cosine" },
	{ cmd_keyword, "acosh", &program::rpn_acosh, "inverse hyperbolic cosine" },
	{ cmd_keyword, "tanh", &program::rpn_tanh, "hyperbolic tangent" },
	{ cmd_keyword, "atanh", &program::rpn_atanh, "inverse hyperbolic tangent" },

	// end
	{ cmd_max, "", NULL, "" },
};