Target Language Compiler

TLC Coding Conventions

These guidelines help ensure that the programming style in each target file is consistent, and hence, more easily modifiable.

Begin Identifiers with Uppercase Letters

All identifiers in the Real-Time Workshop file begin with an uppercase letter. For example,

• NumModelInputs            1
  NumModelOutputs           2
  NumNonVirtBlocksInModel  42
  DirectFeedthrough         yes
  NumContStates             10
  

Block records that contain a Name identifier should start the name with an uppercase letter since the Name identifier is often promoted into the parent scope. For example, a block may contain

• Block {
     :
     :
  RWork            [4, 0]
     :
  NumRWorkDefines   4
  RWorkDefine {
      Name         "TimeStampA"
      Width         1
      StartIndex    0
    }
  }
  

Since the Name identifier within the RWorkDefine record is promoted to PrevT in its parent scope, it must start with an uppercase letter. The promotion of the Name identifier into the parent block scope is currently done for the Parameter, RWorkDefine, IWorkDefine, and PWorkDefine block records.

The Target Language Compiler assignment directive (%assign) generates a warning if you assign a value to an "unqualified" Real-Time Workshop identifier. For example,

• %assign TID = 1
  

produces an error because TID identifier is not qualified by Block. However, a "qualified" assignment does not generate a warning:

• %assign Block.TID = 1
  

does not generate a warning because the Target Language Compiler assumes the programmer is intentionally modifying an identifier since the assignment contains a qualifier.

Begin Global Variable Assignments with Uppercase Letters

Global TLC variable assignments should start with uppercase letters. A global variable is any variable declared in a system target file (grt.tlc, mdlwide.tlc, mdlhdr.tlc, mdlbody.tlc, mdlreg.tlc, or mdlparam.tlc), or within a function that uses the :: operator. In some sense, global assignments have the same scope as Real-Time Workshop variables. An example of a global TLC variable defined in mdlwide.tlc is

• %assign InlineParameters = 1
  

An example of a global reference in a function is

• %function foo() void
    %assign ::GlobalIdx = ::GlobalIdx + 1
  %endfunction
  

Begin Local Variable Assignments with Lowercase Letters

Local TLC variable assignments should start with lowercase letters. A local TLC variable is a variable assigned inside a function. For example,

• %assign numBlockStates = ContStates[0]
  

Begin Functions Declared in block.tlc files with Fcn

When you declare a function inside a block.tlc file, it should start with Fcn. For example:

• %function FcnMyBlockFunc(...)
  

Note    Functions declared inside a system file are global; functions declared inside a block file are local.

Do Not Hard Code Variables Defined in commonsetup.tlc

Since the Real-Time Workshop tracks use of variables and generates code based on usage, you should use access routines instead of directly using a variable. For example, you should not use the following in your TLC file:

• x = %<tInf>;
  

You should use

• x = %<LibRealNonFinite(inf)>;
  

Similarly, instead of using %<tTID>, use %<LibTID()>. For a complete list of functions, see TLC Function Library Reference.

All Real-Time Workshop global variables start with rt and all Real-Time Workshop global functions start with rt_.

Avoid naming global variables in your run-time interface modules that start with rt or rt_ since they may conflict with Real-Time Workshop global variables and functions. These TLC variables are declared in commonsetup.tlc.

This convention creates consistent variables throughout the target files. For example, the Gain block contains the following Outputs function.

Notes about this TLC code:

1. The code section for each block begins with a comment specifying the block type and name.
2. Include a blank line immediately after the end of the function in order to create consistent spacing between blocks in the output code.
3. Try to stay within 80 columns per line for the function banner. You might set up an 80 column comment line at the top of each function. As an example, see constant.tlc.
4. For consistency, use the variables sysIdx and blkIdx for system index and block index, respectively.
5. Use the variable rollVars when using the %roll construct.
6. When naming loop control variables, use sigIdx and lcv when looping over RollRegions and xidx and xlcv when looping over the states.

Example: Output function in gain.tlc

• %roll sigIdx = RollRegions, lcv = RollThreshold, ...
         block, "Roller", rollVars
  

Example: InitializeConditions function in linblock.tlc

• %roll xidx = [0:nStates-1], xlcv = RollThreshold,...
         block, "Roller", rollVars
  

Conditional Inclusion in Library Files

The Target Language Compiler function library files are conditionally included via guard code so that they may be referenced via %include multiple times without worrying if they have previously been included. It is recommended that you follow this same practice for any TLC library files that you yourself create.

The convention is to use a variable with the same name as the base filename, uppercased and with underscores attached at both ends. So, a file named customlib.tlc should have the variable _CUSTOMLIB_ guarding it.

As an example, the main Target Language Compiler function library, funclib.tlc, contains this TLC code to prevent multiple inclusion:

• %if EXISTS("_FUNCLIB_") == 0
  %assign _FUNCLIB_ = 1
    .
    .
    .
  %endif  %% _FUNCLIB_
  

Inlining Fortran (F-MEX) S-Functions

Block Target File Methods