The Formula Node syntax is similar to the syntax used in text-based programming languages. Remember to end assignments with a semicolon (;) as in C. Use scope rules to declare variables in Formula Nodes. Also, keep in mind the allowed functions and the allowed operators and their precedence in the Formula Node.
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Note You can use Formula Node most effectively if you are familiar with the C programming language. LabVIEW Help assumes you are familiar with C and does not contain any topics related to programming in C. Refer to The C Programming Language by Brian W. Kernighan and Dennis M. Ritchie or Teach Yourself C by Herbert Schildt for more information. |
The Formula Node syntax is summarized below using Backus-Naur Form (BNF notation). The summary includes non-terminal symbols: compound-statement, identifier, conditional-expression, number, array-size, floating-point-type, integer-type, left-hand-side, assignment-operator, and function. Symbols in red bold monospace are terminal symbols given exactly as they should be reproduced. The symbol # denotes any number of the term following it.
statement-list:
statement ;
statement ; statement-list
statement:
assignment
compound-statement
control-statement
conditional-statement
iterative-statement
switch-statement
variable-declaration
assignment:
expression
left-hand-side assignment-operator assignment
expression:
expression binary-operator expression
unary-operator expression
expression unary-operator
expression ? expression : expression
( expression )
identifier
constant
function-name ( argument-list )
left-hand-side:
identifier
identifier array-subscription
array-subscription:
[assignment]
[assignment] array-subscription
assignment-operator: one of
= += –= *= /= >>= <<= &= ^= |= %= **=
binary-operator: one of
+ – * / ^ != == > < >= <= && || & | % **
unary-operator: one of
+ – ! ++ –– ~
argument-list:
expression
expression , argument-list
constant:
pi
number
compound-statement:
{ statement-list }
The following table provides the Formula Node syntax for control, conditional, iterative, and switch statements.
| Statement Type | Construct | Grammar | Description/Example |
|---|---|---|---|
| Control Statement | Break Statement | break | Use the break keyword to exit the nearest Do, For, or While Loop or switch statement in the Formula Node. |
| Continue Statement | continue | Use the continue keyword to transfer control to the next iteration of the nearest Do, For, or While Loop in the Formula Node. | |
| Conditional Statement | conditional-statement: if-statement if-else-statement |
if (y==x && a[2][3]<a[0][1]) {
int32 temp; temp = a[2][3]; a[2][3] = y; y=temp; } else x=y; | |
| If Statement | if-statement: if ( assignment ) statement | ||
| If-Else Statement | if-else-statement: if-statement else statement | ||
| Iterative Statement | iterative-statement: do-statement for-statement while-statement |
||
| Do Loops | do statement while ( assignment ) | do {
int32 temp; temp = --a[2]+y; y=y-1; } while (y!=x && a[2]>=a[0]); | |
| For Loops | for ( [assignment] ; [assignment] ; [assignment] ) statement | for (y=5; y<x; y*=2) {
int32 temp; temp = --a[2]+y; x-=temp; } | |
| While Loops | while ( assignment ) statement | while (y!=x && a[2]>=a[0]) {
int32 temp; temp = --a[2]+y; y=y-1; } | |
| Switch Statement | switch ( assignment ) { case-statement-list } | switch(month){
case 2: days = evenyear? 29: 28; break; case 4:case 6:case9: days = 30; break; default: days = 31; break; } | |
| Case Statement List | case-statement-list: case-statement case-statement-list case-statement | ||
| Case Statement | case-statement: case number : statement-list default : statement-list |
variable-declaration:
type-specifier identifier
type-specifier identifier array-index-list
type-spec identifier = assignment
array-index-list:
[integer-constant]
[integer-constant]array-index-list
type-specifier:
floating-point-type
integer-type
floating-point-type:
float
float32
float64
integer-type:
int
int8
int16
int32
uInt8
uInt16
uInt32
non-digit: one of
_ a~z A~Z
digit: one of
0 1 2 3 4 5 6 7 8 9
nonzero-digit: one of
1 2 3 4 5 6 7 8 9
binary-digit: one of
0 1
octal-digit: one of
0 1 2 3 4 5 6 7
hex-digit: one of
0 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F
identifier:
non-digit [non-first-character]
non-first-character:
non-digit [non-first-character]
digit [non-first-character]
number:
integer-constant
float-constant
integer-constant:
decimal-constant
binary-constant
octal-constant
hex-constant
decimal-constant:
nonzero-digit #digit
binary-constant:
0b #binary-digit
0B #binary-digit
octal-constant:
0 #octal-digit
hex-constant:
0x #hex-digit
0X #hex-digit
float-constant:
fraction exponent-part
decimal-constant exponent-part
fraction:
#digit . digit #digit
exponent-part:
e [sign] #digit
E [sign] #digit
sign: one of
+ -
comment:
//comment
/* comment */