diff options
author | Rob Pike <r@golang.org> | 2010-06-14 12:27:22 -0700 |
---|---|---|
committer | Rob Pike <r@golang.org> | 2010-06-14 12:27:22 -0700 |
commit | b9055629c191deab9c4dffc0d0b5f8fb31687e1d (patch) | |
tree | 3a23ff86113f47dea48a8568159935d96878f13a | |
parent | d5a80d0ba4c0e5d9414bca7564a7afd42c3cd072 (diff) | |
download | go-b9055629c191deab9c4dffc0d0b5f8fb31687e1d.tar.gz go-b9055629c191deab9c4dffc0d0b5f8fb31687e1d.zip |
tutorial: update discussion of variadic functions
R=rsc
CC=golang-dev
https://golang.org/cl/1677042
-rw-r--r-- | doc/go_tutorial.html | 21 | ||||
-rw-r--r-- | doc/go_tutorial.txt | 19 |
2 files changed, 25 insertions, 15 deletions
diff --git a/doc/go_tutorial.html b/doc/go_tutorial.html index 40fef30693..7eb09b5b4b 100644 --- a/doc/go_tutorial.html +++ b/doc/go_tutorial.html @@ -938,14 +938,19 @@ implements <code>Printf</code>, <code>Fprintf</code>, and so on. Within the <code>fmt</code> package, <code>Printf</code> is declared with this signature: <p> <pre> - Printf(format string, v ...) (n int, errno os.Error) -</pre> -<p> -That <code>...</code> represents the variadic argument list that in C would -be handled using the <code>stdarg.h</code> macros but in Go is passed using -an empty interface variable (<code>interface {}</code>) and then unpacked -using the reflection library. It's off topic here but the use of -reflection helps explain some of the nice properties of Go's <code>Printf</code>, + Printf(format string, v ...interface{}) (n int, errno os.Error) +</pre> +<p> +The token <code>...</code> introduces a variable-length argument list that in C would +be handled using the <code>stdarg.h</code> macros. +In Go, variadic functions are passed a slice of the arguments of the +specified type. In <code>Printf</code>'s case, the declaration says <code>...interface{}</code> +so the actual type is a slice of empty interface values, <code>[]interface{}</code>. +<code>Printf</code> can examine the arguments by iterating over the slice +and, for each element, using a type switch or the reflection library +to interpret the value. +It's off topic here but such run-time type analysis +helps explain some of the nice properties of Go's <code>Printf</code>, due to the ability of <code>Printf</code> to discover the type of its arguments dynamically. <p> diff --git a/doc/go_tutorial.txt b/doc/go_tutorial.txt index 76dba34efd..6ab6094c02 100644 --- a/doc/go_tutorial.txt +++ b/doc/go_tutorial.txt @@ -622,13 +622,18 @@ We've seen simple uses of the package "fmt", which implements "Printf", "Fprintf", and so on. Within the "fmt" package, "Printf" is declared with this signature: - Printf(format string, v ...) (n int, errno os.Error) - -That "..." represents the variadic argument list that in C would -be handled using the "stdarg.h" macros but in Go is passed using -an empty interface variable ("interface {}") and then unpacked -using the reflection library. It's off topic here but the use of -reflection helps explain some of the nice properties of Go's "Printf", + Printf(format string, v ...interface{}) (n int, errno os.Error) + +The token "..." introduces a variable-length argument list that in C would +be handled using the "stdarg.h" macros. +In Go, variadic functions are passed a slice of the arguments of the +specified type. In "Printf"'s case, the declaration says "...interface{}" +so the actual type is a slice of empty interface values, "[]interface{}". +"Printf" can examine the arguments by iterating over the slice +and, for each element, using a type switch or the reflection library +to interpret the value. +It's off topic here but such run-time type analysis +helps explain some of the nice properties of Go's "Printf", due to the ability of "Printf" to discover the type of its arguments dynamically. |