• Post Reply Bookmark Topic Watch Topic
  • New Topic
programming forums Java Mobile Certification Databases Caching Books Engineering Micro Controllers OS Languages Paradigms IDEs Build Tools Frameworks Application Servers Open Source This Site Careers Other Pie Elite all forums
this forum made possible by our volunteer staff, including ...
Marshals:
  • Campbell Ritchie
  • Jeanne Boyarsky
  • Ron McLeod
  • Paul Clapham
  • Liutauras Vilda
Sheriffs:
  • paul wheaton
  • Rob Spoor
  • Devaka Cooray
Saloon Keepers:
  • Stephan van Hulst
  • Tim Holloway
  • Carey Brown
  • Frits Walraven
  • Tim Moores
Bartenders:
  • Mikalai Zaikin

Executing calculation of an expression within a string

 
Greenhorn
Posts: 5
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
I've got a string containing a mathematical expression. How can I calculate the value of the expression in the string?
Example: stringExp = "4*8";
How can I get the value of 32? I can't figure out how to parse the operator properly.

Thanks
 
Ranch Hand
Posts: 547
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
depends on how complicate your expressions are (e.g. order of operators: 1 + 2 * 3).

you could work with the indexOf() method of String, or the StringTokenizer class or the regular expressions for simple stuff (e.g. just the 4 basic operators without precedence rules).


p
 
Jan Coff
Greenhorn
Posts: 5
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
I'm using the Stringtokenizer and I think I've found a way to do what I need to.

Thanks
 
Rancher
Posts: 43081
77
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
I keep an old piece of code around that evaluates expressions (even with variables) by employing a recursive-descent parser.
 
A wop bop a lu bob a womp bam boom. Tutti frutti ad:
a bit of art, as a gift, the permaculture playing cards
https://gardener-gift.com
reply
    Bookmark Topic Watch Topic
  • New Topic