Calculator program help

I’m trying to make a simple RPN calculator that reads in regular
expressions from a file and evaluates them to execute code. Currently I
have these regular expressions stored in an array of class objects that
have 2 data objects (1. The regex itself and 2. The block of code that
should be executed when a match is found). An example of one of the read
in regex’s is below:

[0-9]+
lambda {|input| $myStack.push(input)}

Now, I get input from the user and compare that string to all the
regular expressions in my array. When a match is found, the code is
evaluated. So far it is working by entering in input one by one. Code
and an example are below.

while input = gets
for i in 0…$regexArray.length-1
if ( input =~ Regexp.new($regexArray[i].regex) )
eval($regexArray[i].code).call(input)
end
end
end

Example:
5
4
+
print

will give “9” as it should. However, I want to make it so I can enter
input in one line like:
5 4 + print

I’ve tried matching the input string with the regex with: myMatch =
regex.match(input)
but when I enter a string such as “123 456” only the last part (“456”)
is matched when I need to first match the (“123”). Any help would be
appreciated.

On Nov 14, 2011, at 10:23 PM, Trevor Daniels wrote:

Now, I get input from the user and compare that string to all the
end

I’ve tried matching the input string with the regex with: myMatch =
regex.match(input)
but when I enter a string such as “123 456” only the last part (“456”)
is matched when I need to first match the (“123”). Any help would be
appreciated.

If your valid expressions contain no whitespace, you can split your
input into individual tokens with split(/\s+/). As a minimal example,
this works fine:

q = []
a = {
/\d+/ => ->(input) { q << input.to_i },
/+|-/ => ->(op) { q.push(q.pop(2).reverse.reduce(op)) },
/print/ => ->(match) { puts q.pop }
}

DATA.each_line do |input|
input.split(/\s+/).each do |token|
code = a[a.keys.detect { |k| token =~ k }]
code.call(token) unless code.nil?
end
end

END
5 4 + print
5 4 - print

Returns 9 and -1.

If you need to parse more complex input on each line, you should use
StringScanner available in the standard library (require ‘strscan’).

On Nov 15, 2011, at 11:05 AM, Sylvester K. wrote:

[0-9]+
eval($regexArray[i].code).call(input)
will give “9” as it should. However, I want to make it so I can enter

code = a[a.keys.detect { |k| token =~ k }]
code.call(token) unless code.nil?
end
end

END
5 4 + print
5 4 - print

Returns 9 and -1.

I’ve just realized, if you’d expect results 9 and 1 then just skip the
#reverse call above :wink:

-----Messaggio originale-----
Da: Sylvester K. [mailto:[email protected]]
Inviato: marted 15 novembre 2011 11:05
A: ruby-talk ML
Oggetto: Re: calculator program help

On Nov 14, 2011, at 10:23 PM, Trevor Daniels wrote:

Now, I get input from the user and compare that string to all the
end

I’ve tried matching the input string with the regex with: myMatch =
regex.match(input)
but when I enter a string such as “123 456” only the last part (“456”)
is matched when I need to first match the (“123”). Any help would be
appreciated.

If your valid expressions contain no whitespace, you can split your
input
into individual tokens with split(/\s+/). As a minimal example, this
works
fine:

q = []
a = {
/\d+/ => ->(input) { q << input.to_i },
/+|-/ => ->(op) { q.push(q.pop(2).reverse.reduce(op)) },
/print/ => ->(match) { puts q.pop }
}

DATA.each_line do |input|
input.split(/\s+/).each do |token|
code = a[a.keys.detect { |k| token =~ k }]
code.call(token) unless code.nil?
end
end

END
5 4 + print
5 4 - print

Returns 9 and -1.

If you need to parse more complex input on each line, you should use
StringScanner available in the standard library (require ‘strscan’).


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-----Messaggio originale-----
Da: Trevor Daniels [mailto:[email protected]]
Inviato: luned 14 novembre 2011 22:24
A: ruby-talk ML
Oggetto: calculator program help

I’m trying to make a simple RPN calculator that reads in regular
expressions
from a file and evaluates them to execute code. Currently I have these
regular expressions stored in an array of class objects that have 2 data
objects (1. The regex itself and 2. The block of code that should be
executed when a match is found). An example of one of the read in
regex’s is
below:

[0-9]+
lambda {|input| $myStack.push(input)}

Now, I get input from the user and compare that string to all the
regular
expressions in my array. When a match is found, the code is evaluated.
So
far it is working by entering in input one by one. Code and an example
are
below.

while input = gets
for i in 0…$regexArray.length-1
if ( input =~ Regexp.new($regexArray[i].regex) )
eval($regexArray[i].code).call(input)
end
end
end

Example:
5
4
+
print

will give “9” as it should. However, I want to make it so I can enter
input
in one line like:
5 4 + print

I’ve tried matching the input string with the regex with: myMatch =
regex.match(input)
but when I enter a string such as “123 456” only the last part (“456”)
is
matched when I need to first match the (“123”). Any help would be
appreciated.


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