TCL scripting language foundation (2)

One 、 brief introduction
Tcl It's a kind of quilt EDA Scripting languages widely supported by the tool , Usually as EDA The tool shell practical .Tcl Extremely XDC Extension enables users to take advantage of Tcl Language in VIvado Complete some series of development operations on , To complete the path 、 The clock 、 Multiple constraints on ports , So as to realize FPGA Design engineering test and correction . Here is a brief introduction to these statements , Concrete XDC Special sentences are explained in other articles .

Two 、Tcl Variable
stay Tcl in , All variables are controlled by ASCII String representation . Variable usage set Command to assign , Its use format is as follows ：

set a 1234;    # notes ： take 1234 Assign a value to a variable a

Using symbols $ Variables can be processed , Replace the assigned value with , And when it is {} Inside , It has no special meaning . As shown below ：

set a 1;    # hold 1 Assigned to a variable a
set b {
    $a}; # hold $a Assign to b
puts a;     # Print out characters a
puts $a;    # Print out a Given value 1
puts b;     # The result is $a

If you add an index after a variable name , Then the variable is automatically converted to an array , The index can be a number , It could be a string ：

set a(1) 1;    # Array a The index of 1 The value of is assigned as 1
puts $a(1);    # The printed result is 1
puts $a;       # If no index is given , Is invalid ;
set a(b) 2;    # Array a The index of b The value of is assigned to 2

You must pay special attention when buying here $ Usage of , He converts variables into their actual values .

3、 ... and 、Tcl list
A list is a collection of objects , You can add 、 Search and other operations .

1. List creation

set gates [list AND OR NOT NAND NOR];
set gates [{
    AND} {
    OR} {
    NOT} {
    NAND} {
    NOR}];
set gates [split "AND.OR.NOT.NAND.NOR" "."];

All three methods above can create a Tcl list , As can be seen from the above example ：

1、list Keywords created for the list ;
2、AND OR After escaping the parentheses {} After escaping, it is assigned to the list as a normal string ;
3、split Represents the string cutting function , Its return value is list .

2. List operation keywords ：lappend、lsearch
lappend Add a new element to the list ：

set  List name  [lappend  List name   Specific elements ];

lsearch Realize whether there is a specific element in the search list , If there is , Returns the index , If it doesn't exist , return -1

lsearch $ List name   Element name ;

Four 、Tcl Expressions and operators
1. Expression evaluation
Expression evaluation uses keywords expr

expr  function   Numbers ;
 Example ：set x 10;
      expr $x+10; Get the results 20

2. Self adding keywords ： incr

incr  Variable   Numbers ;

Add variables to numbers , The result is assigned to the variable .

3. Operator list
Tcl Operators supported in

Operator	describe
-、 +、 ~ 、！	One dollar minus 、 One yuan plus 、 According to the not 、 Logic is not
+ 、-、 *、 /	Add 、 reduce 、 ride 、 except
**	Index
<、> 、<=、 >= 、==、 !=	Less than 、 Greater than 、 Less than or equal to 、 Greater than or equal to 、 be equal to 、 It's not equal to
eq、ne	Compare two strings equal 、 It's not equal to
in、ni	The checklist contains 、 Operators without strings
&、	、^
&&	Logic and
<<、>>	Move left 、 Move right

5、 ... and 、 Control flow statement
1. List traversal
List traversal uses foreach structure

foreach  Variable name  $ List name [];

In parentheses, guard the circular body , All elements in the list will be traversed , The element value is assigned to the variable defined in the statement .

2.if sentence

if{
     Discriminant }
    {
     sentence }
elseif{
     Discriminant }
    {
     sentence }
else
    {
     sentence }

Tcl Provides break and contiune Two keywords are related to If Sentence combination , For loop control .

3.for sentence

for  initial value   Discriminant   Step change 
    {
     Execute statement }

4.while sentence

while  Conditions 
{
     Execute statement }

5. The process （ function ） Definition

proc  The process of {
     Parameters 1  Parameters 2 ...}
{
     The process of body 
    return  parameter }