SPECIAL SYMBOLS
cl
Assignment Arrow +
The assignment arrow causes APL to evaluate everything to the right of the arrow
and associate that value with the name to the left of the arrow. For example,
A+2+3 means that 2+3, or 5, is assigned to the name A. When A is used in a later
APL statement, it has a value of 5.
[:I
Branch Arrow -f
The branch arrow is used for the following:
To change the order in which the statements are executed in a user-defined
function. See Branching in Chapter 6 for more information on branching.
To resume execution of a suspended function (see Suspension in Chapter 7).
To clear the state indicator (see Stare lndicaror in Chapter 7).
The quad is used to ask for input and to display output. To display output, the quad
must appear immediately to the left of the assignment arrow. The value of the APL
expression to the right of the arrow is assigned to the quad and will be displayed.
For example:
'7
1.2
The 7 displayed is the value assigned to the quad. The 12 is the final evaluation of
the APL expression.
When used to ask for input, the quad can appear anywhere except to the immediate
left of the assignment arrow. Execution of the expression stops at the quad and re-
sumes when an expression is entered to replace the quad. When a quad is encountered,
the quad and colon symbols (0 : ) are displayed to indicate that input is requested.
For example:
See Chapter 6 for more information on quad input or output within a user-defined
function.
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Quad Quote pJ (TJJ
The quad quote symbol is formed by overstriking the quote symbol 1 and the quad
symbol 0. The quad quote operates the same way as the quad when requesting
input, except that the data entered is treated as character data. For example:
Note: If a system command is entered for a quad quote input request, the system
command is treated as a character string and will not be executed.
See Chapter 6 for more information on quad quote input or output within a user-
defined function.
Comment A
I:] r;7
The comment symbol is formed by overstriking the n symbol and the 0 symbol.
The comment symbol must be the first nonblank character in a line and indicates
that the line should not be
executed. For example:
(I;
121