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  1. #!/usr/bin/perl
  2. use 5.016;
  3. use warnings;
  4.  
  5. sub factorial { $_[0] < 1 ? $_[1] : factorial($_[0] - 1, $_[1] * $_[0]) }
  6.  
  7. sub rest { [ @{$_[0]}[1 .. $#{$_[0]}] ] }
  8.  
  9. sub term {
  10. 	my ($t, $args) = @_;
  11.  
  12. 	given($t->[0]){
  13. 		when('log('){
  14. 			return sub {
  15. 				my ($t, $x) = @_;
  16. 				($t->[0] eq ')') or die;
  17. 				return (rest($t), log($x));
  18. 			}->(expr(rest($t), $args));
  19. 		}
  20. 		when('sqrt('){
  21. 			return sub {
  22. 				my ($t, $x) = @_;
  23. 				($t->[0] eq ')') or die;
  24. 				return (rest($t), sqrt($x));
  25. 			}->(expr(rest($t), $args));
  26. 		}
  27. 		when(/[0-9]+/){
  28. 			return (rest($t), $t->[0]);
  29. 		}
  30. 		when(/[a-z]+/){
  31. 			return (rest($t), $args->{$t->[0]});
  32. 		}
  33. 	}
  34.  
  35. 	die;
  36. }
  37.  
  38. sub fact {
  39. 	my ($t, $args) = @_;
  40.  
  41. 	return sub{
  42. 		my ($t, $x) = @_;
  43. 		return (($t->[0] eq '!') ? (rest($t), factorial($x, 1)) : ($t, $x));
  44. 	}->(term($t, $args));
  45. }
  46.  
  47. sub pow {
  48. 	my ($t, $args) = @_;
  49.  
  50. 	return sub{
  51. 		my ($t, $x) = @_;
  52. 		return (
  53. 			($t->[0] eq '^') ?
  54. 				sub{ $_[0], $x ** $_[1] }->(fact(rest($t), $args)) :
  55. 				($t, $x)
  56. 		);
  57. 	}->(fact($t, $args));
  58. }
  59.  
  60. sub expr {
  61. 	my ($t, $args) = @_;
  62.  
  63. 	return sub{
  64. 		my ($t, $x) = @_;
  65. 		return (
  66. 			($t->[0] eq '*') ?
  67. 				sub{ $_[0], $x * $_[1] }->(pow(rest($t), $args)) :
  68. 				($t, $x)
  69. 		);
  70. 	}->(pow($t, $args));
  71. }
  72.  
  73. sub interpret {
  74. 	my ($code, $args) = @_;
  75.  
  76. 	my $t = [ $code =~ m/\G\s*([0-9]+|[\!\)\^\*]|log\(|sqrt\(|[a-z]+)/g, '' ];
  77.  
  78. 	return (expr($t, $args))[1];
  79. }
  80.  
  81.  
  82. my @code = split(/\n/, <<'EOF');
  83. 2^n
  84. 2^log(n)
  85. 4^n
  86. n
  87. n^2
  88. n!
  89. n*log(n)
  90. log(n!)
  91. log(log(n))
  92. sqrt(log(n))
  93. EOF
  94.  
  95. my $args = {n => 10};
  96.  
  97. say map{ "$_->[0] = $_->[1]\n" }
  98. 	sort{ $b->[1] <=> $a->[1] }
  99. 	map{ [ $_ => interpret($_, $args) ] } @code;
  100.  
Success #stdin #stdout 0s 3740KB
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n! = 3628800
4^n = 1048576
2^n = 1024
n^2 = 100
n*log(n) = 23.0258509299405
log(n!) = 15.1044125730755
n = 10
2^log(n) = 4.9334096679146
sqrt(log(n)) = 1.51742712938515
log(log(n)) = 0.834032445247956
https://ideone.com/GshPeG
language:
Perl (perl 5.28.1)
created:
10 years ago
visibility:
public

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