test_gamma = ->
  run_test [
    "Gamma(a)",
    "Gamma(a)",

    #  "float(gamma(10))",
    #  "362880",

    "Gamma(x+1)",
    "x*Gamma(x)",
    
    "Gamma(1/2)",
    "pi^(1/2)",
    
    "Gamma(x-1)-Gamma(x)/(-1+x)",
    "0",

    "Gamma(-x)",
    "-pi/(x*Gamma(x)*sin(pi*x))",
    
  ]