How to: grep an Array of strings

[Jason McConochie]

Is there grep for an Array of AbstractStrings?  See code below

# A. Read a file into memory (nLines pre-determined)

fID=open(fName)

iLine=0;

rLines=Array(ASCIIString,nLines);

while !eof(fID)

  iLine+=1

  rLines[iLine]=readline(fID)

end

# B. Find all strings in rLines with "parameter"

???? Is something like this possible?

indices=grep(rLines,r"parameter")

[Erik Schnetter]

You are looking for `filter`:

filter(line->match(r"parameter", line), rLines)

-erik

--

Erik Schnetter <schn...@gmail.com> http://www.perimeterinstitute.ca/personal/eschnetter/

[David P. Sanders]

El jueves, 3 de diciembre de 2015, 13:54:01 (UTC-6), Erik Schnetter escribió:

You are looking for `filter`:

filter(line->match(r"parameter", line), rLines)

Apparently this needs to be

filter(line->ismatch(r"3", line) != nothing, rLines)  

(replace "match" with "ismatch" to get a Boolean expression instead of a RegexMatch object).

[Seth]

If you don't like regexes,

julia> a = ["apple","bear","ape","collar"]
4-element Array{ASCIIString,1}:
 "apple"
 "bear"
 "ape"
 "collar"


julia> filter(x->contains(x,"ap"),a)
2-element Array{ASCIIString,1}:
 "apple"
 "ape"


julia> filter(x->contains(x,"ar"),a)
2-element Array{ASCIIString,1}:
 "bear"
 "collar"

[Stefan Karpinski]

You can just pass a Regex object to filter:

filter(r"a.*b.*c"i, map(chomp,open(readlines,"/usr/share/dict/words")))

This gives all dictionary words containing "a", "b" and "c" in order but not contiguous.

[Seth]

That's really elegant. Is there a reason filter() is defined for regex strings but not ASCIIStrings?

[Stefan Karpinski]

There's an obvious predicate implied by a Regex: does it match a string? What's the obvious predicate for a string? Checking whether it is contained in another string is one option but that's pretty arbitrary. You could just as well check for containment the other way. Or prefix, or suffix, etc.

[Seth]

Makes sense. Thanks!

[Jason McConochie]

Thank you to all.  In particular, how can the indices of the matching lines be returned - I've a matlab background so am used to working from the indices.

[Seth]

One way using my previous code:

julia> find(x->contains(x,"ap"),a)
2-element Array{Int64,1}:
 1
 3

julia> find(x->contains(x,"ar"),a)
2-element Array{Int64,1}:
 2
 4