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clean up the mess that copyright notices make

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Rob Pike 2009-10-13 17:17:30 -07:00
parent cb1ad7e765
commit cd7062ef6f
3 changed files with 415 additions and 437 deletions
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@ -26,7 +26,7 @@ Hello, World
Let's start in the usual way: Let's start in the usual way:
--PROG progs/helloworld.go --PROG progs/helloworld.go /package/ END
Every Go source file declares, using a "package" statement, which package it's part of. Every Go source file declares, using a "package" statement, which package it's part of.
The "main" package's "main" function is where the program starts running (after The "main" package's "main" function is where the program starts running (after
@ -52,13 +52,13 @@ Echo
Next up, here's a version of the Unix utility "echo(1)": Next up, here's a version of the Unix utility "echo(1)":
--PROG progs/echo.go --PROG progs/echo.go /package/ END
This program is small but it's doing a number of new things. In the last example, This program is small but it's doing a number of new things. In the last example,
we saw "func" introducing a function. The keywords "var", "const", and "type" we saw "func" introducing a function. The keywords "var", "const", and "type"
(not used yet) also introduce declarations, as does "import". (not used yet) also introduce declarations, as does "import".
Notice that we can group declarations of the same sort into Notice that we can group declarations of the same sort into
parenthesized, semicolon-separated lists if we want, as on lines 3-6 and 10-13. parenthesized, semicolon-separated lists if we want, as on lines 4-10 and 14-17.
But it's not necessary to do so; we could have said But it's not necessary to do so; we could have said
const Space = " " const Space = " "
@ -85,11 +85,11 @@ a naming conflict.
Given "os.Stdout" we can use its "WriteString" method to print the string. Given "os.Stdout" we can use its "WriteString" method to print the string.
Having imported the "flag" package, line 8 creates a global variable to hold Having imported the "flag" package, line 12 creates a global variable to hold
the value of echo's "-n" flag. The variable "n_flag" has type "*bool", pointer the value of echo's "-n" flag. The variable "n_flag" has type "*bool", pointer
to "bool". to "bool".
In "main.main", we parse the arguments (line 16) and then create a local In "main.main", we parse the arguments (line 20) and then create a local
string variable we will use to build the output. string variable we will use to build the output.
The declaration statement has the form The declaration statement has the form
@ -352,7 +352,7 @@ object. We could write
return n return n
but for simple structures like "File" it's easier to return the address of a nonce but for simple structures like "File" it's easier to return the address of a nonce
composite literal, as is done here on line 17. composite literal, as is done here on line 21.
We can use the factory to construct some familiar, exported variables of type "*File": We can use the factory to construct some familiar, exported variables of type "*File":
@ -370,9 +370,9 @@ multi-value return as a parenthesized list of declarations; syntactically
they look just like a second parameter list. The function they look just like a second parameter list. The function
"syscall.Open" "syscall.Open"
also has a multi-value return, which we can grab with the multi-variable also has a multi-value return, which we can grab with the multi-variable
declaration on line 27; it declares "r" and "e" to hold the two values, declaration on line 31; it declares "r" and "e" to hold the two values,
both of type "int64" (although you'd have to look at the "syscall" package both of type "int64" (although you'd have to look at the "syscall" package
to see that). Finally, line 28 returns two values: a pointer to the new "File" to see that). Finally, line 35 returns two values: a pointer to the new "File"
and the error. If "syscall.Open" fails, the file descriptor "r" will and the error. If "syscall.Open" fails, the file descriptor "r" will
be negative and "NewFile" will return "nil". be negative and "NewFile" will return "nil".
@ -406,7 +406,7 @@ set of such error values.
We can now use our new package: We can now use our new package:
--PROG progs/helloworld3.go --PROG progs/helloworld3.go /package/ END
The import of ''"./file"'' tells the compiler to use our own package rather than The import of ''"./file"'' tells the compiler to use our own package rather than
something from the directory of installed packages. something from the directory of installed packages.
@ -424,12 +424,12 @@ Rotting cats
Building on the "file" package, here's a simple version of the Unix utility "cat(1)", Building on the "file" package, here's a simple version of the Unix utility "cat(1)",
"progs/cat.go": "progs/cat.go":
--PROG progs/cat.go --PROG progs/cat.go /package/ END
By now this should be easy to follow, but the "switch" statement introduces some By now this should be easy to follow, but the "switch" statement introduces some
new features. Like a "for" loop, an "if" or "switch" can include an new features. Like a "for" loop, an "if" or "switch" can include an
initialization statement. The "switch" on line 14 uses one to create variables initialization statement. The "switch" on line 18 uses one to create variables
"nr" and "er" to hold the return values from "f.Read()". (The "if" on line 21 "nr" and "er" to hold the return values from "f.Read()". (The "if" on line 25
has the same idea.) The "switch" statement is general: it evaluates the cases has the same idea.) The "switch" statement is general: it evaluates the cases
from top to bottom looking for the first case that matches the value; the from top to bottom looking for the first case that matches the value; the
case expressions don't need to be constants or even integers, as long as case expressions don't need to be constants or even integers, as long as
@ -441,7 +441,7 @@ in a "for" statement, a missing value means "true". In fact, such a "switch"
is a form of "if-else" chain. While we're here, it should be mentioned that in is a form of "if-else" chain. While we're here, it should be mentioned that in
"switch" statements each "case" has an implicit "break". "switch" statements each "case" has an implicit "break".
Line 21 calls "Write()" by slicing the incoming buffer, which is itself a slice. Line 25 calls "Write()" by slicing the incoming buffer, which is itself a slice.
Slices provide the standard Go way to handle I/O buffers. Slices provide the standard Go way to handle I/O buffers.
Now let's make a variant of "cat" that optionally does "rot13" on its input. Now let's make a variant of "cat" that optionally does "rot13" on its input.
@ -466,7 +466,7 @@ we have a second implementation of the "reader" interface.
--PROG progs/cat_rot13.go /type.rotate13/ /end.of.rotate13/ --PROG progs/cat_rot13.go /type.rotate13/ /end.of.rotate13/
(The "rot13" function called on line 38 is trivial and not worth reproducing.) (The "rot13" function called on line 42 is trivial and not worth reproducing.)
To use the new feature, we define a flag: To use the new feature, we define a flag:
@ -478,7 +478,7 @@ and use it from within a mostly unchanged "cat()" function:
(We could also do the wrapping in "main" and leave "cat()" mostly alone, except (We could also do the wrapping in "main" and leave "cat()" mostly alone, except
for changing the type of the argument; consider that an exercise.) for changing the type of the argument; consider that an exercise.)
Lines 52 through 55 set it all up: If the "rot13" flag is true, wrap the "reader" Lines 56 through 59 set it all up: If the "rot13" flag is true, wrap the "reader"
we received into a "rotate13" and proceed. Note that the interface variables we received into a "rotate13" and proceed. Note that the interface variables
are values, not pointers: the argument is of type "reader", not "*reader", are values, not pointers: the argument is of type "reader", not "*reader",
even though under the covers it holds a pointer to a "struct". even though under the covers it holds a pointer to a "struct".
@ -532,7 +532,7 @@ We can apply "Sort" to any type that implements "Len", "Less", and "Swap".
The "sort" package includes the necessary methods to allow sorting of The "sort" package includes the necessary methods to allow sorting of
arrays of integers, strings, etc.; here's the code for arrays of "int" arrays of integers, strings, etc.; here's the code for arrays of "int"
--PROG progs/sort.go /type.*IntArray/ /swap/ --PROG progs/sort.go /type.*IntArray/ /Swap/
Here we see methods defined for non-"struct" types. You can define methods Here we see methods defined for non-"struct" types. You can define methods
for any type you define and name in your package. for any type you define and name in your package.
@ -711,7 +711,7 @@ channel, and a prime number. It copies values from the input to the
output, discarding anything divisible by the prime. The unary communications output, discarding anything divisible by the prime. The unary communications
operator "<-" (receive) retrieves the next value on the channel. operator "<-" (receive) retrieves the next value on the channel.
--PROG progs/sieve.go /Copy/ /^}/ --PROG progs/sieve.go /Copy.the/ /^}/
The generator and filters execute concurrently. Go has The generator and filters execute concurrently. Go has
its own model of process/threads/light-weight processes/coroutines, its own model of process/threads/light-weight processes/coroutines,
@ -736,7 +736,7 @@ together:
--PROG progs/sieve.go /func.main/ /^}/ --PROG progs/sieve.go /func.main/ /^}/
Line 25 creates the initial channel to pass to "generate", which it Line 29 creates the initial channel to pass to "generate", which it
then starts up. As each prime pops out of the channel, a new "filter" then starts up. As each prime pops out of the channel, a new "filter"
is added to the pipeline and <i>its</i> output becomes the new value is added to the pipeline and <i>its</i> output becomes the new value
of "ch". of "ch".
@ -752,7 +752,7 @@ channel, launches a goroutine internally using a function literal, and
returns the channel to the caller. It is a factory for concurrent returns the channel to the caller. It is a factory for concurrent
execution, starting the goroutine and returning its connection. execution, starting the goroutine and returning its connection.
The function literal notation (lines 8-12) allows us to construct an The function literal notation (lines 12-16) allows us to construct an
anonymous function and invoke it on the spot. Notice that the local anonymous function and invoke it on the spot. Notice that the local
variable "ch" is available to the function literal and lives on even variable "ch" is available to the function literal and lives on even
after "generate" returns. after "generate" returns.
@ -787,7 +787,7 @@ code that invokes the operation and responds to the request:
--PROG progs/server.go /type.binOp/ /^}/ --PROG progs/server.go /type.binOp/ /^}/
Line 10 defines the name "binOp" to be a function taking two integers and Line 18 defines the name "binOp" to be a function taking two integers and
returning a third. returning a third.
The "server" routine loops forever, receiving requests and, to avoid blocking due to The "server" routine loops forever, receiving requests and, to avoid blocking due to