A Recital Primer
Contents
A Recital Primer
Keywords
There are no reserved words in Recital. Command names can be used as variables names. At first glance these seems strange, but provides for greater flexibility when declaring and referencing memory variables and database field variables, as you do not need to concern yourself about names that may already be used as commands.
As an extreme example, the following code will compile and run. It will output "hello"
procedure if(if) return if if = "hello" if if = "hello" echo if( if ) endif
Lines and Indentation
Tabs and spaces have no significance in Recital. Recital commands can begin on any column of a line. A newline ends the command. If you have particularly long commands, you can them extend over multiple lines by placing the line continuation character ; (semicolon) at the end of each line that is to be continued.
echo "This is a one line command" echo "This is a ; multi line ; command"
For better code readability it is recommended that you indent code blocks such as if statements, for loops etc.
// indented code if much more readable and easier to maintain for i=1 to 10 name = "hello world" if name = "hello world" // indent like this endif endfor
Comments
Single line comments
// allows comment lines to be inserted in programs to enhance their readability and maintainability. The // command allows all characters following it on a line, to be treated as a comment and to be ignored by Recital. The // command can be placed anywhere on a line, even following an executable command.
// declare variables private x,y,z
Multi line comments
/* and */ denote block comments. These can be inserted in programs to enhance their readability and maintainability.
The /* denotes the start of the comment block, the */ the end of the comment block.
All characters between the two comment block delimiters are treated as comments and ignored by Recital.
/* the following lines are multi line comments */ private x,y,z
Variables
Variables in Recital do not need to be explicitly declared, although they should be for better code readability and maintainability. When an expression is assigned to a variable, if the variable does not already exist then it will be created implicitly unless SET STRICT ON is in effect.
private x x = 10 // x already exists y = 10 // y does not yet exist so it is created set strict on z = 10 // error is thrown as z does not exist and STRICT is ON
Simple Variables
Variable names must begin with a letter (A-Z, a-z) or an underscore (-), followed by any combination of letters, digits or underscores. The variable name can be of any length, but only the first 32 characters are significant, so these must be unique. Recital ignores the case of letters, so m_var, M_VAR, and m_VaR would all be treated as the same memory variable name. The name given to a variable has no bearing on the type of data that is, or can be, stored in it. In fact, the type of data stored in a particular variable can be changed at any time unless SET STRICT is ON, in which case Recital will type check variables on assigment to them.
m_var = 1234 m_var = 'a character value' ? m_var + 100
Variables can be declared and optionally initialized before used.
private m_var = 1234 m_var = 'a character value' ? m_var + 100
Variables can optionally be declared as specific datatype.
private m_var as numeric = 1234 m_var = 'a character value' /// throws an error
Static Arrays
A static array is an ordered list of elements (variables) that is of a fixed size (number of elements). You declare a static array by specifying the number of elements when you declare a variable.
private tab[ 20 ] // declare a static array of 20 elements all initialized to False // iterate through the array (note the use of the alen( ) function to find the length of the array for i=1 to alen( tab ) // change each array element to hold a numeric value tab[ i ] = i endfor
You can initialize a static array with one statement.
// declare the array and init all elements to false declare tab[10, 10] // init all elements to zero tab = 0
You can create and initialize static arrays using static array initializers.
// simple one dimensional array with 2 elements private tab = { "Hello", "world" } // two-dimensional array of two rows with three columns in each row private tab2 = { { "Hello", 10, date() ], { "world", 20, date()+1 } } // create an array on the fly mytab = { 10, 20, 30, 40, 50, 60 }
You can view the contents of a static array using the echo or ? commands.
? tab
Associative Arrays
An associative array (also known as a dynamic array) is a collection of key/value pairs where the key can be used to retrieve the value. Associative arrays are dynamic, meaning that elements can be added and removed dynamically.
private tab[] // note the use of [] to denote a dynamic array tab["name"] = "bill" tab["age"] = 25 tab["dob"] = date()
Associative arrays can be created and initialized in one statement using the array( ) function.
tab = array("name" => "bill", "age" => 25, ""dob" => date())
You can view the contents of an associative array using the echo or ? commands.
? tab
Objects and Classes
The define class command is used to define a class. Within the define class...enddefine block all aspects of the class – its name, events, methods and properties can be specified.
define class <classname as character> [as <baseclass as character> | custom] [<propertyname1 as character>[, <propertyName2 as character> ...]] [<object>.]<propertyname> = <value as expression> ...] [add object <objectname as character> as <baseclass as character> [with <property-list>]] [function | procedure <procname as character>[_access | _assign] <command statements> [endfunc | endproc]] enddefine
The createobject() function is used to create an object based on a defined class.
object = createobject(<classname as character> [, <arg1 as expression>[, <arg2 as expression> ...]])
Example
define class myclass as custom myprop = "Hello World" enddefine myobject = createobject("myclass") Messagebox(myobject.myprop) addproperty(myobject, "myprop2", "goodbye") // Or: myobject.addproperty("myprop2", "goodbye") Messagebox(myobject.myprop2) removeproperty(myobject, "myprop2") // Or: myobject.removeproperty("myprop2")
Operators
Arithmetic operators
| Operator | Type | Description |
|---|---|---|
| + | addition | returns the first value added to the second |
| - | subtraction | returns the second value subtracted from the first |
| * | multiplication | returns the first value multiplied by the second |
| * | division | returns the first value divided by the second |
| % | modulus | returns the remainder of the first value divided by the second |
| ^ | exponential | returns the first value to the power of the second |
| ** | exponential | returns the first value to the power of the second |
| += | shorthand addition | adds the first value to the second |
| -= | shorthand subtraction | subtracts the second value from the first |
| *= | shorthand multiplication | multiplies the first value by the second |
| /= | shorthand division | divides the first value by the second |
| %= | shorthand modulus | divides the first value by the second and returns the remainder |
Assignment operator
| Operator | Type | Description |
|---|---|---|
| = | assigment | evaluates the expression on the right hand side and stores in the target variable on the left hand side |
String operators
| Operator | Type | Description |
|---|---|---|
| + | concatenate | concatenates the second value to the first |
| - | concatenate trimmed | concatenates the second value to the first after trimming spaces from the end of the first |
| || | concatenate | concatenates the second value to the first after converting to character |
Comparison operators
| Operator | Type | Description |
|---|---|---|
| = | equals | returns true if the first value is equal to the second. |
| == | equals | returns true if the first value is exactly equal to the second or matches the pattern specified in the second value. |
| != | not equals | returns true if the first value is not equal to the second |
| # | not equals | returns true if the first value is not equal to the second |
| <> | not equals | returns true if the first value is not equal to the second |
| < | less than | returns true if the first value is less than the second |
| > | greater than | returns true if the first value is greater than the second |
| <= | less than or equal | returns true if the first value is less than or equal to the second |
| >= | less than | returns true if the first value is greater than or equals to the second |
| $ | contained in | returns true if the left hand side is contained in the right hand side |
| | | contains | returns true if the right hand side is contained in the left hand side |
| ? | sounds like | returns true if the second value sounds like the first |
Logical operators
| Operator | Type | Description |
|---|---|---|
| and | logical and | returns true if first and second values are both true |
| or | logical or | returns true if either first or second values are true |
| xor | logical xor | returns true if either first or second values are true but not both |
| not | logical not | returns the inverse if the right hand side value |
| ! | logical not | returns the inverse if the right hand side value |
Increment and Decrement operators
| Operator | Type | Description |
|---|---|---|
| ++var | pre-increment | returns value after incrementing the variable |
| var++ | pre-increment | returns current value before incrementing the variable |
| --var | pre-decrement | returns value after decrementing the variable |
| var-- | post-decrement | returns current value before decrementing the variable |
Constants
Variables each have a type determined by the data they contain. You can initialize variables by assigning constants into them. Constants each have a primitive type and are the building blocks for all data in Recital
String constants
The string type is used for textual characters. There is no type for representing just one character. A string is a series of zero or more characters. You delimit string constants using either a double-quote " or a single-quote '.
myvar = "This is a string" myvar = 'so is this'
Numeric constants
Numeric types in Recital are all stored as floating point numbers with zero or more decimal places.
myvar = 10 myvar = 10.5678
You can also define hexadecimal numeric constants.
myvar = 0x0aDate constants
Date constants are delimited by curly braces.
// set myvar to 10th of october 2009 myvar = {10/10/2009}
Logical constants
Logical (boolean) constants have one of two values, true or false. The result of any logical comparison expression results in a logical type.
myvar = true myvar2 = false if myvar or myvar2 // this will be executed as myvar is true endif
Currency constants
Currency constants are preceeded by a $.
// set myvar to 1000 dollars myvar = $1000
Datetime constants
Datetime constants are delimited by curly braces.
// set myvar to 10th of october 2009 at 8.30am myvar = {10/10/2009 08:30}
Expressions
Expressions and Statements are the building blocks of Recital programs.
Expressions consists of combinations of operands which can be constant values such as strings, numbers, and dates and operands which are symbols that act on these operands in some way e.g. add two numbers together, concatenate two strings etc.
hello = "Hello" world = "world" hello_world = hello + " " + world result = 100 * 500 / 2 - 6
Operator precedence in expressions
When you have multiple expression terms as in this example:
result = 100 * 500 / 2 - 6
As a general guideline, the operations are performed in the following order.
- Expressions are evaluated from left to right
- Multiplication, division and exponents are performed before addition and subtraction
- Expressions in parentheses are evaluated first
- Mathematical expressions are evaluated before boolean expressions (AND, OR, NOT, XOR)
If in doubt always use parentheses for readability:
result = ((100 * 500) / 2) - 6
Statements
The statement is the basic unit of programming in any programming language. Statements in Recital are delimited by a newline.
echo "Hello world"
You can extend statements over multiple lines by placing a ';' at the end of the line:
echo "Hello ; world" + ; " this is a multi-line statement"
Assigment Statements
The assignment statement stores the result of the expression expression into a variable.
variable = expression
If the variable does not exist and STRICT is OFF, then it is created. If the variable already exists, its contents are updated. If the variable does not exist (has not been declared) and STRICT is ON, then an error is thrown. When STRICT is ON, you should pre-declare variables before assigning values to them using the private, public or local commands.
private myvar set strict on // no error as myvar has already been declared myvar = "hello world" set strict off // error as newvar does not been declared newvar = 10
You can declare and initialize variables in one statement
private myvar = "hello world today is " + cdow( date() )
Recital automatically performs type conversions for variables. If, for example, an existing variable called name contains a character string, and the command name=10 is executed, the variable will automatically be converted to a numeric variable.
If you explicitly tell Recital what type of data can be stored in a variable, it will perform data type checking at runtime.
private myvar as character = "hello world today is " + cdow( date() ) // an error will be thrown because myvar was declared as a character myvar = 10
Control flow statements
The IF command
The if ... endif command is how basic decisions are made in Recital. The if command has a condition and a code body. If the condition evaluates to true then the code body is executed.
name = "bill" if name = "bill" echo "name is bill" endif
The if ... else ... endif command allows for two-way control flow.
name = "bill" if name = "bill" echo "name is bill" else echo "name is not bill" endif
The if ... elseif ... endif command allows for multi-way control flow.
name = "bill" if name = "bill" echo "name is bill" elseif name = "tom" echo "name is tom" elseif name = "mike" echo "name is mike" else echo "unknown name" endif
The DO CASE command
The DO CASE command selects one course of action out of many alternatives. Recital evaluates each CASE condition in turn. As soon as one of the conditions evaluates to true the code body for that CASE is executed and any further case statements are ignored. Following execution of the code body, the program continues after the ENDCASE statement.
OTHERWISE If an OTHERWISE statement is present and no CASE condition evaluates to true the OTHERWISE code body is executed.
ENDCASE If no CASE condition is true and there is no OTHERWISE statement specified, then control skips to the next command following the ENDCASE.
CASE statements, as with all of the other Recital statements can be nested. In other words, a CASE statement can contain further DO CASE commands.
do case case upper(command) = "BROWSE" echo command case upper(command) = "DIR" echo command otherwise echo "Unknown command." endcase
Looping statements
DO WHILE statement
The DO WHILE command repeats the commands between the DO WHILE and the ENDDO statement, until a specified condition becomes false.
do while condition // code body enddo
If the specified condition is true, then all commands within the DO WHILE loop will be executed. If the specified condition is false, then the first statement following the ENDDO will be executed.
If an EXIT statement is encountered then the DO WHILE loop is exited.
If a LOOP statement is encountered, then control returns to the head of the DO WHILE loop.
Statements within the DO WHILE must be properly nested.
// scan through a database table displaying information about an event use events seek "OPERA" do while event = "OPERA" echo event, seats*price skip enddo
FOR statement
for var = startvalue to endvalue [step stepvalue] // commands endfor
The FOR ... ENDFOR command repeats the commands between the FOR and the ENDFOR statement.
The startvalue specifies the loop start point and endvalue the loop end point. These may be numeric or date values.
The FOR...ENDFOR command is equivalent to a counter based DO WHILE ... ENDDO set of commands but FOR ... NEXT is faster.
If the optional STEP stepvalue is specified, then the FOR ... ENDFOR loop will increment by stepvalue. This value can be a positive or negative number. If stepvalue is not specified then the FOR ... ENDFOR loop will increment by 1.
The looping will continue until either endvalue is reached or an EXIT command is encountered.
If a LOOP command is encountered, then control returns to the start of the FOR ... ENDFOR loop.
for i = 1 to 10 step 2 if i % 1 = 1 loop endif echo i*2 endfor
FOREACH statement
The FOREACH command simply gives an easy way to iterate over arrays. FOREACH works on arrays and objects, and will issue an error when you try to use it on a variable with a different data type or an uninitialized variable.
There are two syntaxes; the second is a minor but useful extension of the first:
// static array private myarray = { "hello", "world" } foreach myarray as value echo value endfor // associative array private myarray = array("Name" => "Recital", "Description" => "database") foreach myarray as key => value echo "key=" + key + "value=" + value endfor
The first form loops over the array myarray. On each loop, the value of the current element is assigned to value and the internal array pointer is advanced by one (so on the next loop, you'll be looking at the next element).
The second form does the same thing, except that the current element's key will be assigned to the variable key on each loop. This form works only on associative arrays and objects.
Macros
Variable macro substitution
The & macro function substitutes the contents of the specified variable into the command line. To use a macro in the middle of a word, it is necessary to end the variable name with a '.'. Any type of memory variable can be substituted as a macro.
subscript = 10 i10i = 5 ? i&subscript.i 5
Expression macro substitution
The & macro function can also substitute the result of an expression into the command line. The expression must be enclosed in round brackets.
subscript = "1" i10i = 5 ? i&(subscript + "0")i 5 str1 = "hello" str2 = "world" echo "&str1 &str2" // output "hello world"
Shell command output substitution
Recital provides tight integration with the unix/linux command shell. The ` ... ` command sequence (backticks) can be used to run external shell commands that are piped together and to substitute the output into a Recital character string.
echo "The default directory is `pwd`" echo "There are `ls -l *.dbf | wc -l` tables in this directory"
Functions
Defining a Function
The function command is used to declare a User Defined Function (UDF). Recital UDFs can be used wherever a built-in Recital function can be used.
A UDF can have a variable number of parameters passed to it. These are assigned to private variables in the the <parameter-list> declaration or parameters statement. The parameters() function can be used to determine how many actual parameters were specified.
The function command is terminated with an endfunc or return statement.
function <name as character>[(<parameters as list>)] [parameters <parameters as list>] [return <value as expression> | endfunc]
Calling a Function
Functions can be included in program files, as well as in procedure library files. The functions in a procedure library file are made known to the Recital process by using the set procedure command.
set procedure to [<filename as character> [ADDITIVE]]
Functions can be called like built-in functions: postfixing the name of the function with brackets containing any arguments, e.g.
myudf(m_var,"Hello World",123.45,{12/03/2010})
In this case, parameters are passed by value: a copy of the memory variable is passed to the module and the original memory variable is not accessible within the called module.
Alternatively, the function can be called using the do command and specifying the arguments in the with clause, e.g.
do myudf with m_var,"Hello World",123.45,{12/03/2010}
With do command, parameters are passed by reference: the called module is given the address of the memory variable so the memory variable itself can be altered.
Libraries
Libraries of shareable procedures and functions can be accessed using the set procedure command as described above.
set procedure to [<filename as character> [ADDITIVE]]
The set procedure command opens the specified library file, scans the contents of it, and records the names and positions of the procedures and functions defined within it. You can place as many procedures and functions as you want in a procedure library file.
If the optional ADDITIVE keyword is specified then any libraries that are already open are left open and the new library is added. You can open up to 10 libraries at any one time. The set procedure to command, without any <filename> specified, closes all active library files. A closed library file discards any knowledge of where the procedures within reside. The close procedure command provides the same functionality. The active procedures and functions can be listed with the list procedure command.
