Selection Sort in Algol68

Published on 29 January 2023 (Updated: 01 February 2023)

Welcome to the Selection Sort in Algol68 page! Here, you'll find the source code for this program as well as a description of how the program works.

Current Solution

``````MODE PARSEINT_RESULT = STRUCT(BOOL valid, INT value, STRING leftover);
MODE PARSEINTLIST_RESULT = STRUCT(BOOL valid, REF []INT values);

PROC parse int = (REF STRING s) PARSEINT_RESULT:
(
BOOL valid := FALSE;
REAL r := 0.0;
INT n := 0;
STRING leftover;

# Associate string with a file #
FILE f;
associate(f, s);

# On end of input, exit if valid number not seen. Otherwise ignore it #
on logical file end(f, (REF FILE dummy) BOOL:
(
IF NOT valid THEN done FI;
TRUE
)
);

# Exit if value error #
on value error(f, (REF FILE dummy) BOOL: done);

# Convert string to real number #
get(f, r);

# If real number is in range of an integer, convert to integer. Indicate integer is valid if same as real #
IF ABS r <= max int
THEN
n := ENTIER(r);
valid := (n = r)
FI;

# Get leftover string #
get(f, leftover);

done:
close(f);
PARSEINT_RESULT(valid, n, leftover)
);

PROC count list items = (STRING s) INT:
(
INT count := 1;
FOR k TO UPB s
DO
IF s[k] = ","
THEN
count +:= 1
FI
OD;

count
);

PROC parse int list = (REF STRING s) PARSEINTLIST_RESULT:
(
BOOL valid := FALSE;
STRING leftover := s;
INT num list items = count list items(s);
HEAP [num list items]INT values;

# Repeat while valid value #
FOR k TO num list items
DO
# Get next integer value and update leftover string #
PARSEINT_RESULT result = parse int(leftover);
valid := valid OF result;
leftover := leftover OF result;

# Append the integer value to list #
values[k] := value OF result;

# Do nothing if end of string #
IF leftover = ""
THEN
SKIP
# Skip comma if leftover string starts with comma #
ELIF leftover[1] = ","
THEN
leftover := leftover[2:]
# Otherwise indicate invalid #
ELSE
valid := FALSE
FI
UNTIL NOT valid
OD;

PARSEINTLIST_RESULT(valid, values)
);

PROC usage = VOID: (
printf((\$gl\$, "Usage: please provide a list of at least two integers to sort in the format ""1, 2, 3, 4, 5"""))
);

PROC selection sort = (REF []INT values) VOID:
(
COMMENT
Source: https://en.wikipedia.org/wiki/Selection_sort#Implementations
COMMENT

INT n = UPB values;
INT temp;
INT min pos;
FOR i TO n - 1
DO
min pos := i;
FOR j FROM i + 1 TO n
DO
IF values[j] < values[min pos]
THEN
min pos := j
FI
OD;

IF min pos /= i
THEN
temp := values[i];
values[i] := values[min pos];
values[min pos] := temp
FI
OD
);

PROC show list values = (REF []INT values) VOID:
(
INT n = UPB values;
FOR k TO n
DO
IF k > 1
THEN
print(", ")
FI;

print(whole(values[k], 0))
OD;

IF n > 0
THEN
print(newline)
FI
);

# Parse 1st command-line argument #
STRING s := argv(4);
PARSEINTLIST_RESULT list result := parse int list(s);
REF []INT values := values OF list result;
IF NOT valid OF list result OR UPB values < 2
THEN
usage;
stop
FI;

# Do selection sort and show results #
selection sort(values);
show list values(values)

``````

Selection Sort in Algol68 was written by:

• rzuckerm

If you see anything you'd like to change or update, please consider contributing.

How to Implement the Solution

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How to Run the Solution

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