FIND Function

Material prepared from `M Programming Book`_ (Page 64) [WALTERS1997] [1] and `GT.M Programmer’s Guide`_

$FIND

The $FIND function is a special function built into M to allow you to search strings for certain substrings. You call call $FIND in one of three ways:

$FIND
$F

And it accepts any sort of capitalization: $Find, $find, $f, $FInd, $FiNd, are all syntactically correct, though they may not abide by the style guidelines of your project.

The $FIND function takes two or three arguments as input:

$FIND("Hello","el")
$FIND("Hello","el",2)

$FIND(STRING1,STRING2)
$FIND(STRING1,STRING2,INT)
  • The first argument is the string which is searched through.
  • The second argument is the substring to find inside of the first argument.
  • The third argument is an integer which specifies a starting position for the search.

It should be noted that as a special function, you cannot use $FIND as a command, for instance:

$FIND("PIE", "cake")

is not a valid line of M code, you can only use it in conjunction with a line command, like in the following examples:

GTM>WRITE $FIND("I am a pidgeon","p")
9
GTM>SET X=$FIND("I am a cat","a c")

GTM>WRITE X
9
GTM>WRITE $FIND("I can plant a tree on the moon","e", 20)
26

The $FIND function will return one of three things: * If it finds a substring, it returns the index after the last character in the substring, index+1. * If it does not find the substring, it returns zero. Examples:

GTM>WRITE $FIND("I","I")
2
GTM>WRITE $FIND("I","A")
0

It is important to note that M, unlike C, includes whitespace in it’s syntax, so that you cannot have a space after the comma seperating your arguments:

GTM>WRITE $FIND("I", "A")

Will break on you.

参照

$FIND page at GT.M Programmer’s Guide

[1]Book was unavailable at specified page at the time of writing.

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