More ideas in the outline.
author |
Steve Losh <steve@stevelosh.com> |
date |
Wed, 04 Apr 2012 13:45:32 -0400 |
parents |
c40a55cd4ae4 |
children |
69162b499ec1 751620ce9fae |
Numbers
=======
Now it's time to start taking a closer look at the different types of variables
you can use. First we'll go over Vim's numeric types.
Vimscript has two types of numeric variables: Numbers and Floats. A Number is
a 32 bit signed integer. A Float is, obviously, a floating point number.
Number Formats
--------------
You can specify Numbers in a few different ways. Run the following command.
:::vim
:echom 100
No surprises here -- Vim displays "100". Now run this command:
:::vim
:echom 0xff
This time Vim displays "255". You can specify numbers in hex notation by
prefixing them with `0x` or `0X`. Now run this command:
:::vim
:echom 010
You can also use octal by starting a number with a `0`. Be careful with this,
because it's easy to make mistakes. Try the following commands:
:::vim
:echom 017
:echom 019
Vim will print "15" for the first command, because "17" in octal is equal to
"15" in decimal. For the second command Vim treats it as a decimal number, even
though it starts with a `0`, because it's not a valid octal number.
Because Vim silently does the wrong thing in this case, I'd recommend avoiding
the use of octal numbers when possible.
Float Formats
-------------
Floats can also be specified in multiple ways. Run the following command:
:::vim
:echo 100.1
Notice that we're using `echo` here and not `echom` like we usually to. We'll
talk why in a moment.
Vim displays "100.1" as expected. You can also use exponential notation. Run
this command:
:::vim
:echo 5.45e+3
Vim displays "5450.0". A negative exponent can also be used. Run this command:
:::vim
:echo 15.45e-2
Vim displays "0.1545". The `+` or `-` before the power of ten is optional, if
it's omitted the it's assumed to be positive. Run the following command:
:::vim
:echo 15.3e9
Vim will display "1.53e10", which is equivalent. The decimal point and number
after it are *not* optional. Run the following command and see that it crashes:
:::vim
:echo 5e10
Coercion
--------
When you combine a Number and a Float through arithmetic, comparison, or any
other operation Vim will cast the Number to a Float, resulting in a Float. Run
the following command:
:::vim
:echo 2 * 2.0
Vim displays "4.0".
Division
--------
When dividing two Numbers, the remainder is dropped. Run the following command:
:::vim
:echo 3 / 2
Vim displays "1". If you want Vim to perform float point division one of the
numbers needs to be a Float, which will cause the other one to be coerced to
a Float as well. Run this command:
:::vim
:echo 3 / 2.0
Vim displays "1.5". The "3" is coerced to a Float, and then normal floating
point division is performed.
Exercises
---------
Read `:help Float`. When might floating point number not work in Vimscript?
Read `:help floating-point-precision`. What might this mean if you're writing
a Vim plugin that deals with floating point numbers?