Skip to content

!for

For-loop control structure for automated creation of model source code

Abbreviated syntax (cannot be nested)

In the abbreviated syntax, the control name is simply ?

!for tokens !do
    template
!end

Full syntax

!for ?controlName = tokens !do
    template
!end

Full syntax with Matlab expression

!for ?controlName = <matlab> !do
    template
!end

Description

Use the !for control structure to specify a template and let the Iris preparser automatically create multiple instances of the template by iterating over a list of tokens. The preparser cycles over the individual strings from the list; in each iteration, the current string is used to replace all occurences of the control variable in the template. The name of the control name is either implicitly a question mark, ?, in the abbreviated syntax, or any string starting with a question mark and not containing blank spaces, question marks (other than the leading question mark), colons or periods; for example, ?x, ?#, ?NAME+.

The tokens (text strings) in the list must be separated by commas, blank spaces, or line breaks and they themselves must not contain any of those. In each iteration,

  • all occurrences of the control variable in the template are replaced with the currently processed token;

  • all occurrences in the template of ?.controlName are replaced with the currently processed token converted to lower case; this option is NOT available with the abbreviated syntax;

  • all occurrences in the template of ?:controlName are replaced with the currently processed token converted to upper case; this option is NOT available with the abbreviated syntax;

The list of tokens can be based on Matlab expressions Matlab expressions that evaluates to a list of strings: Enclose an expression in a pair of angle braces, <...>. The expression must evaluate to either a numeric vector, a char vector, a string vetor, or a cell array of numerics and/or strings; the value will be then converted to a comma-separted list of strings.

Examples

Automate similar equations

In a model sourc file, instead of writing a number of definitions of growth rates like the following ones

dP = P/P{-1} - 1;
dW = W/W{-1} - 1;
dX = X/X{-1} - 1;
dY = Y/Y{-1} - 1;

can use the !for control structure as follows:

!for P, W, X, Y !do
    d? = ?/?{-1} - 1;
!end

Also with declarations

We redo the previous example, but using now the fact that you can have as many variable declaration sections or equation sections as you wish. The !for control structure can therefore not only produce the equations for you, but also declare the respectie variables.

!for P, W, X, Y !do
    !transition_variables
        d?
    !transition_equations
        d? = ?/?{-1} - 1;
!end

The preparser expands this structure as follows:

!transition_variables
    dP
!transition_equations
    dP = P/P{-1} - 1;
!transition_variables
    dW
!transition_equations
    dW = W/W{-1} - 1;
!transition_variables
    dX
!transition_equations
    dX = X/X{-1} - 1;
!transition_variables
    dY
!transition_equations
    dY = Y/Y{-1} - 1;

Switch lower/upper case as needed

In a model source file, instead of writing a number of autoregression processes like the following ones

X = rhox*X{-1} + ex;
Y = rhoy*Y{-1} + ey;
Z = rhoz*Z{-1} + ez;

use a !for control structure as follows changing the lower/upper case of the tokens as needed:

!for
    ?# = X, Y, Z
!do
    ?# = rho?.#*?{-1} + e?.#;
!end

Example

Redo the previous example, but now for six variables named A1, A2, B1, B2, C1, C2, nesting two !for control structures one within the other:

!for ?letter = A, B, C !do
    !for ?number = 1, 2 !do
        ?letter?number = rho?.letter?number * ?letter?number{-1} e?.letter?number;
    !end
!end

The preparser produces the following six equations:

A1 = rhoa1*A1{-1} + ea1;
A2 = rhoa2*A2{-1} + ea2;
B1 = rhob1*B1{-1} + eb1;
B2 = rhob2*B2{-1} + eb2;
C1 = rhoc1*C1{-1} + ec1;
C2 = rhoc2*C2{-1} + ec2;

Use Matlab expressions

We use a Matlab expression (the colon operator) to simplify the list of tokens. The following block of code

!for 1, 2, 3, 4, 5, 6, 7 !do
    a? = a?{-1} + res_a?;
!end

can be simplified as follow:

!for <1 : 7> !do
    a? = a?{-1} + res_a?;
!end

or generalized with the use of Matlab variable name supplied through the option assign= when reading the model source file.

!for <1 : N> !do
    a? = a?{-1} + res_a?;
!end