Unicon Language Reference Clinton L. Jeffery Shamim Mohamed ...

7 Operators and Built-in Functions
Icon’s built-ins operators and functions utilize automatic type conversion to provide flexibility
and ease of programming. Automatic type conversions are limited to integer, real, string, and
cset data types. Conversions to a ”number” will convert to either an integer or a real, depending
whether the value to be converted has a decimal. Conversions between numeric types and csets
go through an intermediate conversion to a string value and are not generally useful.
Indexes start at 1. Index 0 is the position after the last element of a string or list. Negative
indexes are positions relative to the end. Subscripting operators and string analysis functions can
take two indices to specify a section of the string or list. When two indices are supplied, they
select the same string section whether they are in ascending or descending order.
7.1 Operators
The result types of operators are the same as the operand types except as noted.
7.2 Unary operators
! x : any* generate elements
The generate operator produces the elements of x. If x is a string variable or refers to a structure
value, the generated elements are variables that may be assigned. !i is equivalent to (1 to i)
for integer i. List, record, string, and file elements are generated in order, with string elements
consisting of one-letter substrings. Set and table elements are generated in an undefined order.
If x is a messaging connection to a POP server, !x produces complete messages as strings. Other
types of files, including network connections, produce elements consisting of text lines.
/ x null test
\ x nonnull test
The null and nonnull tests succeed and produce their operand if it satisfies the test.
- number negate
+ number numeric identity
Negation reverses the sign of its operand. Numeric identity does not change its operand’s value
other than to convert to a required numeric type.
= string tab/match
The tab/match operator is equivalent to calling tab(match(s)) on its operand.
* x : integer size
The size operator returns the number of elements in string, cset or structure x.
. x : x dereference
The dereference operator returns the value x.
? x : any random element
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