KLEL-EXPR(1) libklel KLEL-EXPR(1)NAMEklel-expr - Compile and execute a KL-EL expression
SYNOPSISklel-expr [{-d|--debug-output}] {-e|--expression} expression
klel-expr {-v|--version}
Note: Command line arguments are position dependent, and argument
snuggling (e.g., '-de') is not supported. All arguments and their
values (if any) must be separated by whitespace.
DESCRIPTIONklel-expr executes a single KL-EL expression (see klellang(3)) and
displays its result. User-provided expressions have full access to the
variables and functions exported by KL-EL standard library (see
klelstdlib(3)).
Executing Value Expressions
klel-expr will execute a value expression (see klellang(3)) by
calculating its value and displaying the result.
Executing Guarded Commands
klel-expr will execute a guarded command (see klellang(3)) by testing
the guard. If the guard succeeds (i.e., evaluates to Boolean true),
the command is executed using the specified interpreter, which can be
one of echo or system.
The echo interpreter takes an arbitrary number of string arguments and
echos them back to the display separated by whitespace.
The system interpereter takes a single string argument, passes that
string unchanged to system(3), and displays the output (if any) of the
executed command.
MODES OF OPERATION
The modes of operation described in this section are mutually
exclusive. In other words, only one mode may be specified per
invocation.
{-e|--expression} expression
Compile and execute the specified expression.
{-v|--version}
Display version information and exit.
OPTIONS
{-d|--debug-output}
Print additional debug output during program execution.
RETURN VALUES
Upon successful completion, a value of 0 (XER_OK) is returned.
Otherwise, one of the following error codes is returned:
· 1 = XER_Usage
· 2 = XER_Setup
· 3 = XER_Out_Of_Memory
· 4 = XER_Execute
· 5 = XER_GuardedCommand
EXAMPLES
The following examples are intended to demonstrate different ways of
invoking klel-expr. Lines prefixed with $ indicate user input within a
Bourne or Bourne-like shell.
Example 1. A simple expression.
In this example, a simple arithmetic expression is evaluated.
$ klel-expr-e '1 + 2'
3
When you run the command shown above, klel-expr will compile the
expression, evaluate it, and then print out the result ('3').
Note that the quotes around the expression are required since klel-expr
accepts only a single expression argument.
Example 2. A simple expression with debug output.
In this example, another arithmetic expression is evaluated. More
importantly, the debug-output option is exercised.
$ klel-expr-d -e '2 * pi + 7 / 42 + entier(299.398)'
KlelType='value expression'
KlelExpr='((2 * pi) + 7 / 42) + entier(299.398)'
KlelExprName='expr(00003e7b)'
KlelExprStatus='pass'
KlelExprType='real'
KlelExprOutput=<<EndOfOutput
305.283
EndOfOutput
When you run the command shown above, klel-expr will compile the
expression, evaluate it, and then print out the result (305.283) along
with additional data that are useful for debugging and/or informational
purposes.
Example 3. Executing a guarded command.
In this example, a guarded command is evaluated and conditionally
executed using system(3).
$ klel-expr-e 'if (true) then eval("system", "echo -n GIGO | sum")'
41101 1
When you run the command shown above, klel-expr will compile the
expression, evaluate it, and conditionally execute the guarded command
('echo -n GIGO | sum'). Since the expression always evaluates to true,
the guarded command will always be executed.
Note that klel-expr supports two interpreters, system and echo. The
system interpreter takes one argument (a string) and passes it to
system(3). The echo interpreter takes an arbitrary number of arguments
(the first of which must be a literal string) and echos them to the
standard output.
Example 4. Executing a named expression.
In this example, a named expression is evaluated.
$ klel-expr-e 'my_expression : 1 + 2.1'
3.1
When you run the command shown above, klel-expr will compile the
expression, evaluate it, and then print out the result (3.1).
Example 5. Using let and variable interpolation.
In this example, a simple expression involving the use of let and
variable interpolation is evaluated.
$ klel-expr-e 'let t = now() in odd(t) ? "%{t} --> odd" : "%{t} --> even"'
1353099233 --> odd
When you run the command shown above, klel-expr will compile the
expression, evaluate it, and then print out the result.
Note how the variable t is expressed as '%{t}' in the ternary, which
allows its value to be interpolated to produce the resulting string
value.
SEE ALSOklelapi(3), klellang(3), klelstdlib(3), kleltut(3)1.1.0 2015-09-16 KLEL-EXPR(1)
