Arithmetic evaluation: Difference between revisions

 

The implementation provides an advanced error handling and skipping blanks and Ada comments (these are taken from the library).

with Ada.Unchecked_Deallocation;

with Parsers.String_Source; use Parsers.String_Source;

);

end Parsers.Simple;

Here is the implementation of the package.

with Ada.Characters.Handling; use Ada.Characters.Handling;

with Ada.Exceptions; use Ada.Exceptions;

 

end Parsers.Simple;

The next is a little test. It reads a line from the keyboard and then evaluates it. The program stops when the input is empty:

with Ada.Exceptions; use Ada.Exceptions;

with Ada.Text_IO; use Ada.Text_IO;

end loop;

end Test_Simple_Parser;

Sample exchange. When the expression is evaluated its range in the source string is indicated. Upon errors, the location of is shown as well:

<pre>

 

{{libheader|Boost.Spirit}}1.8.4

#include <boost/spirit/tree/ast.hpp>

#include <string>

}

};

 

=={{header|D}}==

Following the previous number-operator dual stacks approach, an AST is built while previous version is evaluating the expression value. After the AST tree is constructed, a visitor pattern is used to display the AST structure and calculate the value.

import std.stdio, std.string, std.ctype, std.conv ;

 

"1 + 2*(3 - 2*(3 - 2)*((2 - 4)*5 - 22/(7 + 2*(3 - 1)) - 1)) + 1" ; // should be 60

calcVis((new AST).parse(expression)) ;

 

=={{header|Haskell}}==

 

=={{header|Perl}}==

# Evaluates an arithmetic expression like "(1+3)*7" and returns

# its value.

my ($op, @operands) = @$ast;

$_ = ev_ast($_) foreach @operands;

 

=={{header|Pop11}}==