Does String#scan(/(..)(..)/) produce an array of arrays?

R

RLMuller

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Hi All,

"Programming Ruby" says the following for String#scan at =
http://www.ruby-doc.org/docs/ProgrammingRuby/html/ref_c_string.html#Strin=
g.scan:

a =3D "cruel world"=20

...

a.scan(/(..)(..)/) =BB [["cr", "ue"], ["l ", "wo"]]



I wrote the following to test whether scan actually produced an array or =
arrays:



a =3D "cruel world"=20
ar =3D a.scan(/(..)(..)/)
puts "Type of ar =3D %s of size %d" % [ar.class, ar.size]
ix=3D0
ar.each {|x| puts "Type of ar[#{ix}] is %s" % [ix, ar[ix].class]; =
ix+=3D1}


That resulted in:



Type of ar =3D Array of size 2
Type of ar[0] is 0
Type of ar[1] is 1



So it seem like we don't have an array of arrays. So what do we have? =
Or am I all wet?



Regards,
Richard

A programmer is a device for turning coffee into code.
Jeff Prosise (with an assist from Paul Erdos)

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<META http-equiv=3DContent-Type content=3D"text/html; =
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<STYLE></STYLE>
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<BODY bgColor=3D#ffffff>
<DIV><FONT size=3D2>Hi All,</FONT></DIV>
<DIV><FONT size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2>"Programming Ruby" says the following for =
String#scan at <A=20
href=3D"http://www.ruby-doc.org/docs/ProgrammingRuby/html/ref_c_string.ht=
ml#String.scan">http://www.ruby-doc.org/docs/ProgrammingRuby/html/ref_c_s=
tring.html#String.scan</A>:</FONT></DIV>
<DIV><FONT size=3D2></FONT>&nbsp;</DIV>
<DIV>
<P class=3DMsoNormal style=3D"MARGIN: 0in 0in 0pt"><CODE><SPAN=20
style=3D"FONT-SIZE: 10pt; FONT-FAMILY: 'Courier =
New'">a&nbsp;=3D&nbsp;"cruel&nbsp;world"=20
<?xml:namespace prefix =3D o ns =3D =
"urn:schemas-microsoft-com:eek:ffice:eek:ffice"=20
/><o:p></o:p></SPAN></CODE></P>
<P class=3DMsoNormal style=3D"MARGIN: 0in 0in 0pt"><CODE><SPAN=20
style=3D"FONT-SIZE: 10pt; FONT-FAMILY: 'Courier =
New'">...<o:p></o:p></SPAN></CODE></P>
<P class=3DMsoNormal style=3D"MARGIN: 0in 0in 0pt"><CODE><SPAN=20
style=3D"FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">a.scan(/(..)(..)/) =

</SPAN></CODE><FONT face=3D"Times New Roman">=BB&nbsp; =
</FONT><CODE><SPAN=20
style=3D"FONT-SIZE: 10pt; FONT-FAMILY: 'Courier =
New'">[["cr",&nbsp;"ue"],&nbsp;["l&nbsp;",&nbsp;"wo"]]</SPAN></CODE></P>
<P class=3DMsoNormal style=3D"MARGIN: 0in 0in 0pt"><CODE><SPAN=20
style=3D"FONT-SIZE: 10pt; FONT-FAMILY: 'Courier =
New'"></SPAN></CODE>&nbsp;</P>
<P class=3DMsoNormal style=3D"MARGIN: 0in 0in 0pt"><CODE><SPAN=20
style=3D"FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">I wrote the =
following to=20
test whether scan actually produced an array or =
arrays:</SPAN></CODE></P>
<P class=3DMsoNormal style=3D"MARGIN: 0in 0in 0pt"><CODE><SPAN=20
style=3D"FONT-SIZE: 10pt; FONT-FAMILY: 'Courier =
New'"></SPAN></CODE>&nbsp;</P>
<P class=3DMsoNormal style=3D"MARGIN: 0in 0in 0pt"><CODE><SPAN=20
style=3D"FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">a =3D "cruel =
world" <BR>ar =3D=20
a.scan(/(..)(..)/)<BR>puts "Type of ar =3D %s of size %d" % [ar.class,=20
ar.size]<BR>ix=3D0<BR>ar.each {|x| puts "Type of ar[#{ix}] is %s" % [ix, =

ar[ix].class]; ix+=3D1}<BR></SPAN></CODE></P>
<P class=3DMsoNormal style=3D"MARGIN: 0in 0in 0pt"><CODE><SPAN=20
style=3D"FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">That resulted=20
in:</SPAN></CODE></P>
<P class=3DMsoNormal style=3D"MARGIN: 0in 0in 0pt"><CODE><SPAN=20
style=3D"FONT-SIZE: 10pt; FONT-FAMILY: 'Courier =
New'"></SPAN></CODE>&nbsp;</P>
<P class=3DMsoNormal style=3D"MARGIN: 0in 0in 0pt"><CODE><SPAN=20
style=3D"FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'"><FONT =
face=3DArial>Type of ar=20
=3D Array of size 2<BR>Type of ar[0] is 0<BR>Type of ar[1] is=20
1</FONT></P></SPAN></CODE>
<P class=3DMsoNormal style=3D"MARGIN: 0in 0in 0pt"><CODE><SPAN=20
style=3D"FONT-SIZE: 10pt; FONT-FAMILY: 'Courier =
New'"></SPAN></CODE>&nbsp;</P>
<P class=3DMsoNormal style=3D"MARGIN: 0in 0in 0pt"><CODE><SPAN=20
style=3D"FONT-SIZE: 10pt; FONT-FAMILY: 'Courier New'">So it seem like we =
don't=20
have an array of arrays.&nbsp; So what do we have? Or am I all=20
wet?</SPAN></CODE></P>
<P class=3DMsoNormal style=3D"MARGIN: 0in 0in 0pt"><CODE><SPAN=20
style=3D"FONT-SIZE: 10pt; FONT-FAMILY: 'Courier =
New'"></SPAN></CODE>&nbsp;</P></DIV>
<DIV><FONT size=3D2>Regards,<BR>Richard</FONT></DIV>
<DIV>&nbsp;</DIV>
<DIV><FONT size=3D2>A programmer is a device for turning coffee into =
code.<BR>Jeff=20
Prosise (with an assist from Paul Erdos)<BR></FONT></DIV></BODY></HTML>

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H

Hal Fulton

RLMuller said:
Hi All,

"Programming Ruby" says the following for String#scan at
http://www.ruby-doc.org/docs/ProgrammingRuby/html/ref_c_string.html#String.scan:


|a = "cruel world" |

|...|

|a.scan(/(..)(..)/) |» |[["cr", "ue"], ["l ", "wo"]]|

||

|I wrote the following to test whether scan actually produced an array
or arrays:|

||

|a = "cruel world"
ar = a.scan(/(..)(..)/)
puts "Type of ar = %s of size %d" % [ar.class, ar.size]
ix=0
ar.each {|x| puts "Type of ar[#{ix}] is %s" % [ix, ar[ix].class]; ix+=1}
|

|That resulted in:|

||

|Type of ar = Array of size 2
Type of ar[0] is 0
Type of ar[1] is 1|

||

|So it seem like we don't have an array of arrays. So what do we have?
Or am I all wet?|
Click to expand...

You're all wet. ;)

Seriously, you've just made a typo or two. Your last format string does
an interpolation instead of using a format specifier. You're printing
the value of ix as the class.

I suggest each_with_index and consistent formatting, like

ar.each_with_index {|x,ix| puts "Type of ar[#{ix}] is #{ar[ix].class}" }

If you don't like variable interpolation, you can use a real printf:

printf "Type of ar[%d] is %s\n",ix,ar[ix].class

Anyhow, you do get real live arrays here, just as the Book says.

Hal
 
R

Richard

Many thanks, Hal,

As I told you before, I've got your book, but digesting everything in
a book of 579+ pages takes time, as does finding the answer to a
specific question, so thanks for hanging out on this newsgroup.

And thanks for 'drying me out'; I certainly was 'all wet' in my
amateurish mistake. Better still, I'm thankful for your truly
Rubyesque improvement. I learned one more thing, thereby.

Regards,
Richard
 

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