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ID | Project | Category | View Status | Date Submitted | Last Update | |||

0005173 | OCaml | OCaml general | public | 2010-11-04 02:01 | 2013-09-03 17:27 | |||

Reporter | warwick | |||||||

Assigned To | ||||||||

Priority | normal | Severity | feature | Reproducibility | always | |||

Status | closed | Resolution | no change required | |||||

Platform | OS | OS Version | ||||||

Product Version | 3.12.0 | |||||||

Target Version | Fixed in Version | |||||||

Summary | 0005173: Value of Pi and Math module | |||||||

Description | Sorry ... I guess this has been discussed already, but I think the inclusion of a value for Pi would make OCaml easier to learn and use (rather than having to put: let pi = 4. *. atan 1. in your code). It'd be a problem adding pi to the namespace in Pervasives, so it'd be good to have a Math module. This would give the opportunity to move floating point functions from Pervasives to Math, over time; and also the chance to add some new maths functions or values if required - without cluttering Pervasives. For example: Math.round, Math.deg, Math.rad, Math.e, Math.asinh, Math.acosh, Math.atanh, ... | |||||||

Tags | No tags attached. | |||||||

Attached Files | ||||||||

Notes | |

(0005699) warwick (reporter) 2010-11-04 03:59 |
I just looked at the value of pi more closely (using toplevel OCaml 3.12.0 on Mac) and I didn't realise that the floating point loses some precision, so if you put either of let pi = 4. *. atan 1. let pi = 3.1415926535897932384626433832795 You end up with val pi : float = 3.14159265358979312 (ie ending with ...312 rather than ...323 or ...324 rounded) |

(0005704) xleroy (administrator) 2010-11-11 18:21 |
Hello, You're right that, in retrospect, it would have been preferable to have a separate module for float operations in the standard library. Experience shows, however, that adding a new module in the stdlib with a nice, popular name like Math always introduces incompatibilies in existing Caml code, something that we cannot afford at this point. Note, however, that OCaml Batteries (http://thelema.github.com/batteries-included/hdoc/ [^]) has a "BatFloat" module very much like what you propose, and it defines "BatFloat.pi" among other useful things. If you have ideas and code for additional floating-point stuff, I'm sure the Batteries people would be receptive. Concerning the loss of precision: the float you get out of "4 *. atan 1.0" is, indeed, the 64-bit IEEE float closest to the true value of pi. That's the best one can do within the limitations of this float format. |

Issue History | |||

Date Modified | Username | Field | Change |

2010-11-04 02:01 | warwick | New Issue | |

2010-11-04 03:59 | warwick | Note Added: 0005699 | |

2010-11-11 18:21 | xleroy | Note Added: 0005704 | |

2010-11-11 18:21 | xleroy | Status | new => closed |

2010-11-11 18:21 | xleroy | Resolution | open => no change required |

2013-09-03 17:27 | doligez | Relationship added | related to 0004170 |

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