SIMetrix scripts, like all computer programs, process data stored in variables. Variables may hold real, complex or string data and may be scalar - possessing only a single value - or single dimension arrays called vectors.
In this topic:
\ " & + - * / ^ < > ' @ { } ( ) [ ] ! % ; : |=and spaces.
Variables may have real, complex or string type. Real and complex are selfexplanatory. Strings are a sequence of ASCII characters of any length.
SIMetrix does not have an integer type. Although all numbers are represented internally as floating point values, the format used permits integers to be represented exactly up to values of about ???MATH???2^{52}???MATH???.
a | ???MATH???10^{-18}???MATH??? |
f | ???MATH???10^{-15}???MATH??? |
p | ???MATH???10^{-12}???MATH??? |
n | ???MATH???10^{-9}???MATH??? |
u | ???MATH???10^{-6}???MATH??? |
m | ???MATH???10^{-3}???MATH??? |
k | ???MATH???10^{+3}???MATH??? |
Meg | ???MATH???10^{+6}???MATH??? |
G | ???MATH???10^{+9}???MATH??? |
T | ???MATH???10^{+12}???MATH??? |
Complex numbers are represented in the form:
(real, imaginary)
Strings are a sequence of text characters enclosed in single quotation marks. Single quotation marks themselves are represented by two in succession.
2.3 4.6899 45 1e-3 1.2u
(1,1) means 1+i (2.34,10) means 2.34+10i
'this is a string' 'This is a "string"'
Let x=3assigns the value 3 to the variable x. Note that Let is not optional as it is in most forms of Basic.
Let x=(5,1) Let s='This is a string'All of the above are scalar that is they contain only one value. Variables may also be single dimension arrays called vectors. Vectors are described below.
Some characters have a special meaning and if entered into a string literal will not work correctly. Characters affected are newline, tab, semi-colon, single and double quotation and open and close brace characters.
Open and close brace characters ('{' and '}') and semi-colon (';') may be included in a string literal by enclosing the whole string with double quotation marks. (There is more information here Quotes: Single or Double).
Single and double quotation marks can be included by doubling them up. However, this can be inconvenient and an alternative method is to assign a variable with the special character using the Chr function. This method is also the only way to enter a tab character into a literal string. For example:
Let tab = chr(9) Let string = 'This is a tab ' & tab & ' character'
This method can be used to enter new line characters (chr(10)) and also single quotes (chr(39)), double quotes (chr(34)) and semi-colons (chr(59))
[ expression1, expression2, ...]E.g.
let v = [1, 3, 9]These are described in more detail in the section on Bracketed Lists. Functions and simulator vectors are described in following sections.
Vectors, like other variables may also contain strings or complex numbers but all the elements must be the same type.
let v = [1, 3, 9] let a = v[2]a is assigned 9 in the above example. Index values start at 0 so the first element (1) is v[0].
let v[2] = 5In which case the value assigned must have the same type (i.e. real, complex or string) as the other elements in the vector.
Vectors, like other variables may also contain strings or complex numbers but all the elements must be the same type.
Let global:result = 10global:result will be accessible by all scripts and from the command line. Further it will be permanently available until explicitly deleted with UnLet. After the variable has been created with the global: prefix, it can subsequently be omitted. For example in:
Let global:result = 10 Show result Let result = 11 Show resultwill display
result=10 result=11in the message window. The variable result will be available to other scripts whereas if the global: prefix had been left off, it would not. Although it is not necessary to include the global: prefix except when first creating the variable, it is nevertheless good practice to do so to aid readability of the script.
Empty values should not be confused with empty strings. The latter is explained in the next section.
{"}Empty strings are not the same as empty values. An empty value has no data at all and will result in an error if supplied to any function other than the Length function.
Single quotation marks ( ' ) and double quotation marks ( " ) both have a special, but different, meaning in SIMetrix and in the past this has been the source of much confusion. Here we explain what each means and when they should be used. Single quotes are used to signify a text string in an expression. Expressions are used as arguments to the Plot, Curve, Let and Show commands, they are used in braced substitutions and also as the tests for if, for and while statements. These are the only places where you will find or need single quotes. Double quotes are used in commands to bind together words separated by spaces or semi-colons so that they are treated as one. Normally spaces and semi-colons have a special meaning in a command. Spaces are used to separate arguments of the command while semi-colons terminate the command and start a new one. If enclosed within double quotes, these special meanings are disabled and the text within the quotes is treated as a single argument to the command. Double quotes are often used to enclose strings that contain spaces (see example) but this doesn't necessarily have to be the case.
Let PULSE_SPEC = 'Pulse 0 5 0 10n 10n 1u 2.5u'In the above line we are assigning the variable PULSE_SPEC with a string. This is an expression so the string is in single quotes. Let is a command but it is one of the four commands that take an expression as its argument.
Prop value "Pulse 0 5 0 10n 10n 1u 2.5u"Prop is a command that takes a number of arguments. The second argument is the value of a property that is to be modified. In the above line, the new property value, Pulse 0 5 0 10n 10n 1u 2.5u has spaces in it so we must enclose it double quotation marks so that the command treats it as a single string. If there were no quotes, the second argument would be just Pulse and the remainder of the line would be ignored. If an argument contains no spaces or semi-colons then no quotes are necessary although they will do no harm if present.
There are situations where both single and double quotes are needed together. In some of the internal scripts you will find the Scan function used to split a number of text strings separated by semi-colons. The second argument to Scan is a string and must be enclosed in single quotation marks. But this argument is also a semi-colon which, despite being enclosed in single quotes, will still be recognised by the command line interpreter as an end-of-command character. So this must be enclosed in double quotes. The whole expression can be enclosed in double quotes in this case.
If you need a string that contains a double or single quote character, use two of them together.
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