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Manipulating Text

A single piece of text is referred to as a string in the wide world of programming.  A string consists of 1 or more characters from the ASCII table.  The ASCII table assigns an integer (0-255) to each letter, number, and punctuation we see on the screen.  Why?  Because the computer only understands numbers, in fact only zeros and ones - but we won't go there.

Comparisons

The thing about strings are, when you evaluate them - you are evaluating its underlying ASCII value.  For example, we can write:

005

     if 'a' < 'd'

Since the ASCII value of "a" is 97 and "d" is 100, the if statement returns true.  Not knowing this, you may have written:

006     if $asc('a') < $asc('d')

Which is perfectly ok, just long winded.

007     if 'abc' == 'def'

Line #007 - on the first pass, the ASCII value of "a" is compared with the ASCII value of "d".  It does not equal, therefore the if statement is false and "b" and "c" are never evaluated with "e" and "f".

008     if 'ab' < 'af'

Line #008 - on the 1st pass, "a" == "a", but on the 2nd pass, the ASCII value of "b" is compared with the ASCII value of "f".  The ASCII value of "b" is less than "f", therefore the if statement is #true.


Operators

The only basic operator is addition (+) or concatenation.

009     s = 'ARRIS'+'cad'  /* s='ARRIScad'
010     s = 'Sigma'+'Design'+'International'

Line #010 will return "SigmaDesignInternational" - Don't forget spaces!


Dot Operators

Dot operators perform specialize functions.  Character positioning is base1, the first character in the string is position 1.

string = string1 .left. iposition
Returns the left-part of string1, up to and including the (iposition)th character.
016     s = 'ARRIScad'.left.5   /* s='ARRIS'

string = string1 .right. iposition
Returns the (iposition) right-most characters in the string1.
017     s = 'ARRIScad'.right.3  /* s='cad'

string = string1 .from. iposition
Returns all characters to the right of (& including) the (iposition)th character in the string1.
018     s = 'ARRIScad'.from.6   /* s='cad'

string = string1 .pick. iposition
Returns the (iposition)th character in the string1.
019     s = 'ARRIScad'.pick.6   /* s='c'

string = string1 .pos. string2
Returns the beginning position of the first left-most occurrence of string2 in string1.
020     i = 'ARRIScad'.pos.'R'  /* i=2
021     i = 'ARRIScad'.pos.'RR' /* i=2

string = string1 .rpos. string2
Returns the beginning position of the first right-most occurrence of string2 in string1.
022     i = 'ARRIScad'.rpos.'R'         /* i=3
023     i = 'ARRIScad'.rpos.'RRI'       /* i=2


$utilities

There are numerous $utilities that deal with strings.  I'll just quickly list them here, leaving the exploration to you and a much later lesson.

                Returns:
$acs(s1)        ASCII value
$chk(s1)        True if s1 is numeric
$chr(i1)        Character for i1 (ASCII value)
$len(s1)        Number of characters in s1
$str(r1)        Converts a number to a numeric string (r1 to s1)
$trim(s1)       Trims leading and trailing spaces
$val(s1)        Converts a numeric string to a number (s1 to r1)


That's all for now,
Steve

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