embrace

Debraced C code.

Embrace is a program to insert braces into debraced C source code. Debraced C source code selectively has curly braces {...} removed in favor of indentation, similar to Python. This work is inspired by optional braces in Scala 3. There is a nice assessment of optional braces in Scala 3. The described advantages of debracing include:

• "Programs become shorter, clearer, and more beatiful."
• "Writers stay in the flow, no need to go back and forth inserting braces."
• "Program changes are more reliable than with braces."

Indentation is significant in debraced C. Debraced C must only use spaces for indentation, rather than tab characters. The number of spaces per level of indentation is up to the programmer, but the number of spaces for lines on the same indentation level must match.

Embrace re-inserts braces {...} in such a way that the line numbers do not change compared to the debraced source code. Thus line numbers in compiler error messages are the same as in the debraced source code.

The embracing process is transparent to the programmer, because it can be embedded as a rule in the Makefile.

Semicolons ; at the end of lines may optionally be omitted.

Parentheses (...) around the conditions of if statements, forstatements, and whilestatements may be omitted, if the condition is followed by the do keyword. So

if (x < 5) ...

may be written as

    if x < 5 do ...

The condition of a while loop

    while (x < 5) ...

may be written as

    while x < 5 do ...

and a for loop

    for (int i = 0; i < 5; i++) ...

becomes

    for int i = 0; i < 5; i++ do

The do keyword is used in all cases, because it already is a keyword in C and therefore does not clash with variable names.

The end of indented regions may optionally be marked with an end marker. End markers are advisable to improve the readability of longer indented regions or when a region is indented by multiple levels. The end marker of debraced C is end., optionally followed by a token. If it is followed by a token, then the corresponding opening line must contain this token. Here is an example:

    if x < 5 do
        printf("x is less than 5\n")
        ...
        ... many lines
        ...
    end. if

The end marker end. (with a trailing .) makes name collisions unlikely. One may still use end as a variable name, even if it is a struct.

Examples

Here are a few examples. As a convention, debraced C code has the file extension .d.c.

C: count_digits.c

#include <stdio.h>

int main(void) {
    int ndigit[10];
    int i = 0;
    while (i < 10) {
        ndigit[i] = 0;
        i++; 
    }
    while ((i = getchar()) != EOF) {
        if (i >= '0' && i <= '9') {
            ndigit[i - '0']++; 
        }
    }
    i = 0;
    while (i < 10) {
        printf("%d: %4d times\n", i, ndigit[i]);
        i++; 
    }
    return 0; 
}

Debraced C: count_digits.d.c

#include <stdio.h>

int main(void)
    int ndigit[10]
    int i = 0
    while i < 10 do
        ndigit[i] = 0
        i++
    while (i = getchar()) != EOF do
        if i >= '0' && i <= '9' do // with comment
            ndigit[i - '0']++
    i = 0
    while i < 10 do
        printf("%d: %4d times\n", i, ndigit[i])
        i++
    return 0
end. main

C: dowhile.c

#include <stdio.h>

int main(void) {
    int i = 0;
    do {
        printf("%d\n", i);
        i++;
    } while (i < 5);
    return 0;
}

Debraced C: dowhile.d.c

#include <stdio.h>

int main(void)
    int i = 0
    do
        printf("%d\n", i)
        i++
    while (i < 5)
    return 0

Compilation

To compile embrace perform the following steps:

cd embrace
make embrace

To compile an example perform these steps:

cd examples
make dowhile
./dowhile

The Makefile in the examplesdirectory transparently invokes embrace to create a temporary C file, which is then used to compile the program. If you want to see the rebraced C source code, use make dowhile.c. The resulting dowhile.c is:

#include <stdio.h>

int main(void) {
    int i = 0;
    do {
        printf("%d\n", i);
        i++; }
    while (i < 5);
    return 0; }

The unusual placement of braces ensures that line numbers do not change, which is important for compiler error messages.

Tools like astyle may be used to convert this into your preferred style. For example, the .astylerc file in this project produces:

#include <stdio.h>

int main(void) {
    int i = 0;
    do {
        printf("%d\n", i);
        i++;
    } while (i < 5);
    return 0;
}