Erlang and OTP in Action.pdf - Synrc

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User switch command
--> j
1 {shell,start,[init]}
2* {shell,start,[]}
--> k 1
--> j
2* {shell,start,[]}
--> c
When you do this sort of thing, just be very careful about which job it is you’re killing, in
case you have several things in progress in different jobs. When you kill a job, all the history,
previous results and other things associated with that shell job will disappear. To keep better
track of jobs, you can specify a name when you start a new job, that will show up in the list:
--> s important
--> j
2 {shell,start,[]}
3* {important,start,[]}
--> c
We will see more of the Ctrl-G menu in chapter 8 when we talk about distributed Erlang
and how to use remote shells. This is as simple as it is powerful, and is the single most
important tool for remote controlling and debugging production systems.
Now that you have a feel for how to work in the Erlang console, it is time to start playing
around with the actual programming language.
2.2 – Data types in Erlang
Understanding basic data representation conventions is an essential part of learning any
programming language. Erlang’s built-in data types are straightforward and relatively few,
but you can achieve quite a lot with them. Data in Erlang is usually referred to as “terms”.
Do try entering some examples of terms while you read this section. (Don’t forget to add a
period before you press return.) Let’s start with the simplest ones.
2.2.1 – Numbers and arithmetic
Erlang has two numerical data types: integers and floating-point numbers (“floats”).
Conversion is done automatically by most of the arithmetic operations, so you don’t usually
need to do any explicit type coercion.
INTEGERS
Integers in Erlang can be of arbitrary size. If they are small enough, they are represented in
memory by a single machine word; if they get larger (so-called “bignums”), the necessary
space is allocated automatically. This is completely transparent to the programmer, and
means that you never need to worry about truncation or wrap-around effects in arithmetic—
those things simply cannot happen.
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