Befunge-98 - 26 22 21

~:d3*-d2*/1-!" "*+,#@

Basically, it does putchar((c = getc()) + (c > '@' && !(c > 'Z'))*' '), pretending for a moment that the assignment to c is guranteed to happen first and that I got the nesting of parentheses right...

Now, instead it relies on the fact that (c-39)/26 is 1 only for character codes of uppercase ASCII characters (assuming integer division). So instead, I print out c + (((c-39)/26)==1)*' ' for each character c.

Sample session:

% cfunge lower.b98
hello WORLD!
hello world!
This is a TEST!!11 az AZ @[`{
this is a test!!11 az az @[`{

Befunge-98 - 26 22 21 19

~:''-d2*/1-!' *+,#@

Relies on the fact that (c-39)/26 is 1 only for character codes of uppercase ASCII characters (assuming integer division). For each character c, print out c + (((c-39)/26)==1)*' '.

Sample session:

% cfunge lower.b98
hello WORLD!
hello world!
This is a TEST!!11 az AZ @[`{
this is a test!!11 az az @[`{

Befunge-98 - 26 22

~::"@"`\"Z"`!*" "*+,#@

Basically, it does putchar((c = getc()) + (c > '@' && !(c > 'Z'))*' '), pretending for a moment that the assignment to c is guranteed to happen first and that I got the nesting of parentheses right...

Example session:

% cfunge lower.b98
hello WORLD!
hello world!
This is a TEST!!11 az AZ @[`{
this is a test!!11 az az @[`{

Edit: compare with both '@' and 'Z' in turn to shave off a few chars.

Befunge-98 - 26 22 21

~:d3*-d2*/1-!" "*+,#@

Basically, it does putchar((c = getc()) + (c > '@' && !(c > 'Z'))*' '), pretending for a moment that the assignment to c is guranteed to happen first and that I got the nesting of parentheses right...

Now, instead it relies on the fact that (c-39)/26 is 1 only for character codes of uppercase ASCII characters (assuming integer division). So instead, I print out c + (((c-39)/26)==1)*' ' for each character c.

Sample session:

% cfunge lower.b98
hello WORLD!
hello world!
This is a TEST!!11 az AZ @[`{
this is a test!!11 az az @[`{

Befunge-98 - 26

~:"@"-:0`\55*1+`!*" "*+,#@

Basically, it does putchar((c = getc()) + ((c-'@') > 0 && !((c-'@') > 26))*' '), pretending for a moment that the assignment to c is guranteed to happen first and that I got the nesting of parentheses right...

Example session:

% cfunge lower.b98
hello WORLD!
hello world!
This is a TEST!!11 az AZ @[`{
this is a test!!11 az az @[`{

Befunge-98 - 26 22

~::"@"`\"Z"`!*" "*+,#@

Basically, it does putchar((c = getc()) + (c > '@' && !(c > 'Z'))*' '), pretending for a moment that the assignment to c is guranteed to happen first and that I got the nesting of parentheses right...

Example session:

% cfunge lower.b98
hello WORLD!
hello world!
This is a TEST!!11 az AZ @[`{
this is a test!!11 az az @[`{

Edit: compare with both '@' and 'Z' in turn to shave off a few chars.