The purpose of grep is to filter a list. It does so by evaluating a piece of code for each item in the argument list. It wants a yes/no answer from the code it executes, so scalar context is warranted.
The purpose of map is to transform a list. There is no correlation between in the size of the input list and the size of the output list. A given element may be transformed into zero, one or many elements, so list context is warranted.
To tie this back to the subject at hand, this is basically how all operators work:
- If an operator requires exactly one value for an operand (such as either operand of the scalar assignment operator), the operator will impose a scalar context on that operand.
- If an operator requires multiple values for an operand (such as either operand of the list assignment operator), the operator will impose a list context on that operand.
Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
Read Where should I post X? if you're not absolutely sure you're posting in the right place.
Please read these before you post! —
Posts may use any of the Perl Monks Approved HTML tags:
Outside of code tags, you may need to use entities for some characters:
- a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
Link using PerlMonks shortcuts! What shortcuts can I use for linking?
See Writeup Formatting Tips and other pages linked from there for more info.
| & || & |
| < || < |
| > || > |
| [ || [ |
| ] || ] ||