Filter Script Basic is 90% compatible with MS GWBasic and QBasic(TM), with some Pascal extension like While, Repeat, Break, Continue, which let you write programs without labels and Goto instructions. Numeric labels are supported for backward compatibility with old Basic programs
This Basic Script supports Numbers and Strings.
Built-in Basic Functions
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Numeric functions: |
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ABS(n) LN(n) LOG10(n) LOG2(n) EXP(n) RND() RND(n) INT(n) FIX(n) ROUND(n) FRAC(n) SQR(n) SGN(n) SIN(n) COS(n) TAN(n) ASIN(n) ACOS(n) ATAN(n) ATAN2(n,m) SINH(n) COSH(n) TANH(n) ASINH(n) ACOSH(n) ATANH(n) DEGTORAD(n) RADTODEG(n) ASC($) LEN($) VAL($) |
Absolute value Natural logarithm, base e Logarithm, base 10 Logarithm, base 2 Exponential Random number in the range 0..1 Random number in the range 0..n Integer part of n Integer part rounded toward zero Roundation of n Fractional part of n Square root Sign of n, +1 0 -1 Sine of number, radians Cosine Tangent Inverse sine Inverse cosine Inverse tangent Inverse tangent of n/m with right quadrant Hyperbolic sine Hyperbolic cosine Hyperbolic tangent Inverse hyperbolic sine Inverse hyperbolic cosine Inverse hyperbolic tangent Degrees to radians conversion Radians to degrees conversion Ascii code of char Length of string String to number conversion |
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String functions: |
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LCASE$($) UCASE$($) LTRIM$($) RTRIM$($) CHR$(n) STR$(n) HEX$(n) MID$($,n,[n]) LTAB$($) RTAB$($) LEFT$($,n) RIGHT$($,n) INSTR($,substring) |
Lowercase conversion Uppercase conversion Left blanks deletion Right blanks deletion Ascii to char conversion Number to string conversion Number to hexadecimal Substring extraction Left insertion of a Tab Right insertion of a Tab Left part of a string Right part of a string Returns position of substring |
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String functions, Multi Rows: |
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COUNT($) OPENTEXT$($) SAVETEXT$($) COPYTEXT$($) PASTETEXT$($) FINDFILE$($,$) FINDDIR$($,$) |
Count rows in a multi-row string Open a text file into a string Save the string as a text file Copy the string to the clipboard Paste text from clipboard into the string Get a list of files in the directory (dir,extension) Get a list of directories |
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Miscellaneous functions: |
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PAUSE(n) MESSAGE($). |
Suspend execution for n seconds Show a message in a dialog window. |
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Reserved words
if end for goto local print endfunc |
or mod not step while input endwhile |
to cls else break gosub repeat continue |
and rem then endif until return function |
True = -1
False = 0
| Built-in CNC Functions | ||
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addspaces() cancel() changev(address,oldvalue,newvalue,format) closefile() createfile(filename) currentlinenumber() executefile(filename,param) firstline() front(string) hasaddress(address) getvalue(address) getglobalnum(index) getglobal$(index) getlineindex$(index) gotoline(index) insertline(string) ioline$() lastline() linecount() offset(address,value) openfile(filename) output(string) punchleader(inches) punchmanread(string) remove(string) rear(string) rotate(angle) stripcomment() stripspaces() setline(string) scale(address,value) setglobalnum(index,value) setglobal$(index,string) saveprint(filname) sendxon() sendoff() setlineindex$(index,string) stop(string) sendfile(filename) wait(milliseconds) writetofile(string) |
Comments:
REM this is a comment
' and this is too
' but shorter
1# Example: (Pascal-like, recommended style)
for a = 1 to 10 print "Hello" if a > 5 then break next print "the end"
2# Example: (old Basic style)
10 for a = 1 to 10 20 print "Hello" 30 if a > 5 then goto 50 40 next a 50 print "the end"
Loop instructions
Basic Script supports three kinds
of loop instructions.
For, While and Repeat.
The easiest way to understand a Loop instruction
is to look at an example.
The following program prints the numbers 1 to 10, "a" is the control
variable:
FOR a = 1 to 10 PRINT a NEXT a
The BREAK instruction:
terminates instantly a cycle, so in this case the cycle stops when "a"
becomes greater than 5.
FOR a = 1 to 10 PRINT a IF a>5 then BREAK NEXT a
The CONTINUE instruction: acts as a NEXT instruction; the variable "a" is incremented and a new iteration is started immediately.
FOR a = 1 to 10 PRINT a IF a>5 then CONTINUE PRINT "hello" NEXT a
FOR-NEXT instruction:
The complete syntax for this command is:
...
...
NEXT [<variable> (ignored)]
examples: FOR angle = 1+ASIN(0.4) to 1+ASIN(0.75) step 0.1 PRINT angle NEXT
FOR y = 1 to 200 FOR x = 1 to 320 s = s + x*y NEXT NEXT
REPEAT-UNTIL instruction:
This instruction repeats a series of instructions until the condition is
True. The block begins with the REPEAT command and ends with the UNTIL
command followed by the condition that is evaluated.
Example:
a = 1 REPEAT PRINT a a = a+1 UNTIL a>10
The Repeat instruction evaluates the condition at the end of the loop, this means that the instructions inside the loop are executed at least once. The Break and Continue instructions can be used in REPEAT-UNTIL cycles just like in the FOR-NEXT cycles.
WHILE-ENDWHILE
instruction:
This instruction evaluates a condition at the beginning of the loop. If
the condition is false then the cycle stops and execution continues
after the Endwhile instruction.
Example:
a = 1 WHILE a <= 10 PRINT a a = a+1 ENDWHILE
Since the While command evaluates the condition at the beginning of the loop, the instructions inside the loop may be also executed never. The Break and Continue instructions can be used in WHILE-ENDWHILE cycles just like in the FOR-NEXT cycles.
Strings
A string variable contains text. This text may be a
single row or a multi-line text. The maximum theoretical size of a
string variable is 2 Gbyte.
Example:
a$ = "Hello" + "World" + "!"
The value of the variable "a$" is now "HelloWorld!"
String variables are used with operators to perform string expressions
and are used with some functions to Open and Save data from text files.
A single row of a multi-line string con be read using square brackets,
example:
if a$ contains:
" This is a text placed on three rows "
b$ = a$[2]
Now b$ contains: "text placed on"
Numbers
A numeric variable contains a number. The number is internally represented by a floating point value with double precision (64 bit, 15 significant digits).
Numeric variables are used with operators to perform numeric expressions and are used as counters in loop instructions.
Jump instructions
The following instructions (Goto, Gosub, Return) are
supported only for compatibility with Basic.
They cannot be used inside Functions.
Goto instruction:
This instruction jumps at the given label.
Example:
10 if a > 5 then GOTO 30 20 print "a <= 5" 30 print "Script ended"
Gosub - Return instructions: They were used to make subroutines. Now it's better to define a Function. Example:
10 x = 3 : y = 6 20 GOSUB 100 30 print "Result:" ; r 40 end 100 r = sqrt(x^2+ y^2) 110 RETURN
Basic functions
A function is defined as set of instructions that computes and returns a value.
The result can be discarded (like C and Delphi) or simply not returned, making it a procedure. Local variables can be defined to support recursive functions.
Syntax:
Function <Name> ( parameters ) [ Local <local variables> ] ... [Return <result>] ... Endfunc
Examples: FUNCTION sum(a,b) return a+b ENDFUNC
FUNCTION intpower(a,b) LOCAL t,r r=1 for t = 1 to b r = r * a next return r ENDFUNC
FUNCTION hello$(a$) return "Hello to you " + a$ ENDFUNC
Basic fully supports recursive functions, example:
FUNCTION factorial(n) if n <= 1 then return 1 return n*factorial(n-1) ENDFUNC
Conditional instructions
The IF-THEN instruction evaluates a logical expression and determines the flow of the program based on the result of that expression.
Examples of logical expressions:
a > 5 and b > 5 a >= 3 or not b <> 5 and b+3 = c
Precedence of operators:
Higher precedence:
< , > , <= , >= , <> , = NOT AND OR
Lower precedence.
Syntax:
IF <logical expression> THEN ... ... [ELSE] ... ... ENDIF
Compact Syntax:
IF <logical expression> THEN <instruction> : <instruction> ...
IF instructions can be nested without limits; the ELSE
part is optional and is not allowed in the compact syntax.
Examples:
IF a < 0 and a > -10 THEN print "A was a small negative number": a = -a
IF a >= 0 THEN print a IF a = 12 THEN print "A prefect number !" IF a > 1000 THEN print "What a big number" ENDIF ELSE print "Negative numbers not allowed!" ENDIF
Identifiers
Identifiers denote variables and functions.
An identifier can be of any length, must begin with a letter and can't
contain spaces.
String identifiers denote string variables and string
functions.
The last character must be $
examples of valid identifiers:
counter , temp , pix , n , n2 name$ , address2$ , filename$ , a$
Since there is no window to print to in Filter Script,
the print function prints to buffer that can be saved to a file.
See SavePrint function.
Print [ expression [, expression] [; expression] ]
Description:
Every expression must be separated by a semicolon or comma; if semicolon
is used then no spaces are added between the writings. If comma is used
then a TAB separator is added between the writings. Numbers are always
printed preceded by a space.
Example:
PRINT "Some math" ; 3+5 ; 4*4*4 ; sin(2.5)
INPUT Shows a dialog window where the user can enter data.
Input [ <Question> , ] variable
Description:
Use this function to ask the user for input values.
If the user doesn't click the OK button then zero or an empty string is
returned.
Example:
INPUT "How old are you ?", a INPUT "Your name ?", n$ PRINT n$ ; " is"; a
Operators
Operators are classified as arithmetic operators and string operators.
Precedence:
Operators with higher precedence are performed before operators with low
precedence.
Operators with equal precedence are performed from left to right.
Numeric operators
Numeric operators apply in numeric expressions, Basic supports the
following operators:
| + - * / ^ ?> ?< MOD |
Addition Subtraction Multiplication Division Power Maximum Minimum Modulo |
Higher precedence:
( , ) - (unary) ^ * , / , MOD + , - , ?> , ?<
Lower precedence.
Examples:
12 + 15 = 27 12 - 4 = 8 2 ^ 8 = 256 7 * 5 = 35 10 / 4 = 2.5 18 MOD 8 = 2 5 ?> 3 = 5 8 ?< 2 = 2
String operators
String operators apply in string expressions, Basic
supports the following operators:
+ Addition / Addition with New Line - Deletion
Precedence:
String operators have the same precedence and are evaluated from left to
right.
Examples:
"Hello" + "World" = "HelloWorld" "Hello" - 2 = "Hel" "Hello" / "World" =
"Hello World"
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