Perl

1
Perl

• Hour 9More Functionsand Operators

2
Searching Strings

• index string, substr, opt_start
• index We all fall down, all
• returns 3
• index We all fall down, all, 4
• returns 8
• index(strat, z)
• returns -1

3
Searching from right

• rindex string, sub_str, opt_start
• rindex We all fall down, all
• returns 8

4
Substrings

• substr string, start, opt_length
• Use in expression to extract
• Use on left of assignment to replace or insert
  (replace length 0 substring)
• Negative start counts from right
• Negative length ends at that count from right,
  strips last length characters

5
Substring Examples

• a This is a test
• substr a, 5 is a test
• substr a, 5, 2 is
• substr a, -9, -5 is a
• substr(a, 7, 0) not This is not a test

6
Transliteration

• Replace one set of characters with another, by
  position in list
• tr /from/to/ operates on _
• tr /A-Z/a-z/ Note range as lc
• r tr/0-9/./ operates on r
• Last to char repeated to match length
• This form counts replacements in _
• If second slot is empty, no replacement

7
Formatted Printing

• printf as in C
• sprintf too

8
Arrays as Stacks

• Operations on arrays
• push array, new_list on back
• pop array returns last entry
• shift array, new_list on front
• unshift array returns first element
• How can you make a queue?

9
Splicing Arrays

• Similar to substring
• splice array, o_offset, o_length, o_list
• Returns removed part
• Array is truncated to length
• Removed items may be replaced