Thanks On Wednesday, May 10, 2017 at 2:21:54 PM UTC-7, Val wrote: > > Hello Zachary > Stdin and os.Args are quite different. > If your wrote a go program named "kaplan", then when running the following > command on a unix-like system (linux, or OSX) : > > cat bigphoto.jpg | kaplan sepia downscale > result.jpg > > you have os.Args[0]=="kaplan", os.Args[1]=="sepia", > os.Args[2]=="downscale". They are all strings indeed, but it is unlikely > that using them will cause any inefficiency, because the total length of > the command-line arguments is usually small (<1000). > > you also have all the bytes from the contents of the file "bigphoto.jpg" > streamed to the os.Stdin of your program. > os.Stdin is a os.File, which implements io.Reader. It is designed to > handle bytes, not strings. More precisely, you would call os.Stdin.Read to > put the bytes into the []byte of your choice. > > If your func : > - wants to return a short, human-readable text: return a string. > - wants to build a long and immutable human-redable text: make a buf > []byte, fill it, then return string(buf). > - wants to return binary data: return a []byte. > - wants to return text data that the caller will modify: return a []byte. > > Also, you may find interesting (for efficiency) that reslicing a substring > doesn't create a copy : > t := s[30:55] > t shares the same immutable array in memory as s. See video Lexical > Scanning in Go <https://www.youtube.com/watch?v=HxaD_trXwRE> : the whole > lexer may parse the input file as one big string, without ever copying the > tokens characters : tokens are just "slices" of the source code. > > HTH, > Val > > > On Wednesday, May 10, 2017 at 7:15:01 PM UTC+2, Zachary Kaplan wrote: >> >> in golang, strings are immutable. thus, if i want to modify a string in >> place, i'll need to cast or copy each element from the string to a similar >> but mutable data structure. this seems inefficient for simple command line >> programs that take input from stdin and access it through os.Args. can >> somebody please explain to me when a function should to return a string as >> opposed to, say a []byte? thanks >> >
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