Msc. Patran pcl handbook In a Nutshell 7

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Loop Control Statements

For Loop

Syntax

FOR (var=numeric_expr TO numeric_expr [BY numeric_expr]) [label]
statements …
END FOR
E
Square braces [ ], denotes optional
xample

AvgTemp = 0.0
FOR (i = 1 TO NumNodes)
AvgTemp += NodalTemp(i)
END FOR
AvgTemp = AvgTemp/NumNodes

While Loop

Syntax

WHILE (logical_expression) [label]
statements …
END WHILE
Example

AvgTemp = 0.0
i = 1
WHILE (i <= NumNodes)
AvgTemp += NodalTemp(i)
i += 1
END WHILE
AvgTemp = AvgTemp/NumNodes

Loop Control Statements

Repeat Loop

This is similar to a WHILE Loop except that it will always be executed at least once. Only use REPEAT loops if you want to ALWAYS execute the loop at least once, otherwise us a WHILE loop.

Syntax

REPEAT [label]
statements …
UNTIL (logical_expression)
Example

AvgTemp = 0.0
i = 1
REPEAT
AvgTemp += NodalTemp(i)
i += 1
UNTIL (i > NumNodes)
AvgTemp = AvgTemp/NumNodes

Loop Control Statements

BREAK

The BREAK statement is used to exit a loop prior to its normal termination. It can be used in any of the loop statements.

S
If status is not equal to zero, then the end of the file has been reached. Execution then breaks out of the WHILE loop to the statements immediately following the loop.
yntax

BREAK [label]

Example 1(reading a text file)

WHILE (TRUE)

status = text_read_string(…)

IF (status != 0) THEN BREAK
END WHILE
statements

…

Example 2 (nested loops, using labels)

WHILE (i <= NumNodes) MainLoop

WHILE (j <= 100) AnotherLoop

WHILE (k <= 200) InnerLoop

IF (status != 0) THEN BREAK MainLoop

IF (status != 0) THEN BREAK AnotherLoop

IF (status != 0) THEN BREAK

IF (status != 0) THEN BREAK InnerLoop

END WHILE

statements …

END WHILE

statements …
END WHILE

statements

Loop Control Statements

CONTINUE

The CONTINUE statement is used to skip to the end of the loop

Syntax

CONTINUE [label]
Example 1 (reading a text file)

INTEGER file_id, length

STRING read_str[80]

/* read grid information */

WHILE (text_read_string(file_id, read_str, length) == 0)

IF (str_index(read_str, “GRID”) == 0) THEN CONTINUE

statements …
END WHILE
Example 2 (nested loop, using labels)

WHILE (i <= NumNodes) MainLoop

REPEAT InnerLoop

CONTINUE MainLoop

BREAK InnerLoop

CONTINUE

CONTINUE InnerLoop

UNTIL (j > 1000)

statements …

END WHILE

statements …

Exercise 4: Writing Files

The function should have a single argument, the filename to be created, i.e., FUNCTION write_nodes_to_file(FileName)
The data should be written to the file as a table, i.e.,

Node Id x-coordinate y-coordinate z-coordinate

Use virtual arrays
Use the following built-in functions:

db_count_nodes(NumNodes)

db_get_node_ids(NumNodes, NodeIds)

db_get_nodes(NumNodes, NodeIds, rcids, acids, NodeXYZ)

text_open(FileName, Options, idum, idum, FileId)

text_close(FileId, Options)

text_write(FileId, Format, Ints, Reals, Chars)

text_write_string(FileId, OutString)

Use the documentation if you have questions about the arguments to the built-in functions.
Think about your choice for the format argument in the text_write(…) function. Will your file be comma or space delimited? Will it be fixed or free format?
Sample code outline:

Declare variables
Count nodes in the database
Allocate arrays
Get node Ids
Get node coordinates
Open file
Write data to the file with a loop
Close file
Be sure to include a message that the file output is complete

Writing Files

Extra credit: Include a header line at the top of the file that includes the filename and the total number of nodes written to the file.

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